Note: This page contains sample records for the topic radiation graft polymerization from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: November 12, 2013.
1

Functionalization of carbon nanotubes by radiation-induced graft polymerization.  

PubMed

Multi-walled carbon nanotubes (MWCNTs) were functionalized by radiation-induced graft polymerization of acrylic acid onto the surface of MWCNTs in order to improve their dispersibility in water. 1H NMR, Raman spectroscopy, TEM, and TGA techniques were used to characterize the resulting functionalized MWCNTs. The grafting degree was dependent on the grafting conditions such as the absorbed dose and the monomer concentration. The experimental results confirmed that poly(acrylic acid) chains were successfully grafted onto the surface of the MWCNTs. The poly(acrylic acid)-grafted MWCNTs showed a much better water dispersibility than the pristine MWCNTs. PMID:19908742

Jung, Chan-Hee; Kim, Dong-Ki; Choi, Jae-Hak; Shin, Kwanwoo; Nho, Young-Chang; Suh, Dong-Hack

2009-12-01

2

Metal oxides immobilized fabrics by radiation induced graft polymerization  

NASA Astrophysics Data System (ADS)

Radiation induced graft polymerization is effective for adding a new functionality to various forms of existing polymers. Ion-exchange nonwoven fabrics by gamma radiation induced graft polymerization have been used as filters in air and liquid. However, these materials have no capability for removing non-ionic species, such as volatile organic compound and ozone. Manganese oxides immobilized fabrics were developed for removing ozone. In addition, these materials were capable of removing formaldehyde and arsenic. Fine particles of manganese oxides were observed on the fibers. New materials produced by radiation induced graft polymerization and metal immobilization were applicable for purification of contaminants in environment. Manufacturing process is applicable for immobilization of the other metal oxides.

Fujiwara, K.; Masubuchi, T.; Miyata, K.; Shiozawa, M.; Takato, T.; Harakawa, H.

2010-03-01

3

Effect of solvents on radiation-induced ionic graft polymerization. [Gamma radiation  

SciTech Connect

The influence of various solvents on radiation-induced cationic (grafting of vinyl-n-butyl ether onto polyethylene) and anionic (grafting of 2-methyl-5-vinylpyridine onto polyethylene) graft polymerization was studied. This ionic grafting was performed in thoroughly dried systems at room temperature. It was established that electron-acceptor solvents promote cationic grafting but that electron-donor solvents promote the anionic. A clear correlation between the donor number of solvents and grafting value by the anionic mechanism was shown. There was no correlation between dielectric constants and grafting values. The reaction orders, according to monomer concentraton by 2-methyl-5-vinylpyridine grafting in various solvents, were equal to approximately 1.5 and 2 for the radical and anionic mechanisms, respectively. The effect of solvents on radiation-induced ionic graft polymerization is discussed. The results of this study indicate the correct choice of solvents for radiation-induced ionic grafting.

Kabanov, V.Ya.; Aliev, R.E.; Sidorova, L.P.

1980-03-01

4

Radiation-induced graft polymerization of amphiphilic monomers with different polymerization characteristics onto hydrophobic polysilane  

NASA Astrophysics Data System (ADS)

The structures of poly(methyl-n-propylsilane) (PMPrS) amphiphilically modified through ?-ray-induced graft polymerization were investigated with 1H NMR measurement. By the use of methyl methacrylate (MMA) or diethyl fumarate (DEF) as monomers for the graft polymerization, grafting yield rose with increasing total absorption dose and monomer concentrations, but decreased with increasing dose rate. This result means that grafting yield of modified PMPrS can be controlled by changing irradiation conditions. However, the number of PMMA or PDEF graft chains per PMPrS chain was estimated to be less than 1.0 by analysis of 1H NMR spectra, and this value was lower than that we had expected. To improve graft density, maleic anhydride (MAH), which is known as a non-homopolymerizable monomer in radical polymerization, was used as a monomer for grafting. As a result, high density grafting (one MAH unit for 4.2 silicon atoms) was attained. It demonstrates that the structure of ?-ray-modified polysilane strongly depends on the polymerization characteristics of grafted monomers.

Tanaka, Hidenori; Iwasaki, Isao; Kunai, Yuichiro; Sato, Nobuhiro; Matsuyama, Tomochika

2011-08-01

5

Graft polymerization using radiation-induced peroxides and application to textile dyeing  

NASA Astrophysics Data System (ADS)

To improve the dyeing affinity of ultra high molecular weight polyethylene (UHMWPE) fiber, surface treatment by radiation-induced graft polymerization was performed. Methyl methacrylate (MMA), acrylic acid (AA) and styrene (St) were used as the monomers. The grafting yields as a function of storage time after irradiation were examined. Although the grafting yield of St after the sulfonation processing was quite low compared with those of MMA and AA, it was successfully dyed to a dark color with a cationic dye. Some acid dyes can dye the grafted fiber with AA. The acid dye is distributed to the amorphous domains of the AA grafted fiber. The dyeing concentration depended on the grafting yield, and the higher the grafting yield the darker the dye color.

Enomoto, Ichiro; Katsumura, Yosuke; Kudo, Hisaaki; Soeda, Shin

2011-02-01

6

Radiation-Induced Graft Polymerization of Styrene in Wood.  

National Technical Information Service (NTIS)

Grafting of polystyrene to the cellulose in red pine sapwood has been accomplished by gamma irradiation of the ternary solution of styrene, methanol, and water. The resulting material possesses substantially enhanced bending strength and dimensional stabi...

K. V. Ramalingam G. N. Werezak J. W. Hodgins

1964-01-01

7

Ionizing radiation graft polymerized and modified flame retardant cotton fabric  

Microsoft Academic Search

Halogen free flame retardant cotton (FR cotton) fabric was prepared by grafting 2,3-epoxypropyl methacrylate (GMA) on ordinary or untreated cotton (UT cotton) fabric by ?-rays from 60Co source. Epoxy groups present in GMA grafted cotton (GMA-g-cotton) fabric was reacted with ethylene diamine and subsequently modified with orthophosphoric acid solution to convert in to FR cotton fabric. Effects of imparted dose,

P. R. S. Reddy; G. Agathian; Ashok Kumar

2005-01-01

8

Ionizing radiation graft polymerized and modified flame retardant cotton fabric  

NASA Astrophysics Data System (ADS)

Halogen free flame retardant cotton (FR cotton) fabric was prepared by grafting 2,3-epoxypropyl methacrylate (GMA) on ordinary or untreated cotton (UT cotton) fabric by ?-rays from 60Co source. Epoxy groups present in GMA grafted cotton (GMA-g-cotton) fabric was reacted with ethylene diamine and subsequently modified with orthophosphoric acid solution to convert in to FR cotton fabric. Effects of imparted dose, concentration of monomer on grafting percentage were studied. The changes in thermal properties after treatment were investigated by using Thermo gravimetric analyser. Limiting oxygen index, char length, time after glow and time after flame were also studied as per ASTM D2863 and IS11871, respectively, for both FR cotton and UT cotton fabrics. The FR cotton fabric was found to pass all the above tests. Washing durability of the FR cotton fabric in different cleaning agents was also studied and a washing solution containing organic solvent mixture is suggested.

Reddy, P. R. S.; Agathian, G.; Kumar, Ashok

2005-03-01

9

Diffusion control in radiation graft polymerization with varying dependence of rate on monomer concentration  

Microsoft Academic Search

The quantitative effect of diffusion control on the rate of radiation-initiated graft polymerization has been studied theoretically for systems in which the diffusion-free reaction may show various dependencies of rate on monomer concentration other than the usual first-order dependence. The study is also very general in that it can be applied to systems involving a variety of different modes of

Kaya Imre; George Odian; Abdelgewad Rabie

1976-01-01

10

Chemical reactive filter paper prepared by radiation-induced graft polymerization—I  

Microsoft Academic Search

Chelating filter papers with chemically bonded amidoxime groups were synthesized by radiation-induced grafting of acrylonitrile onto filter paper (W3) followed by chemical treatment with hydroxylamine. The effect of grafting conditions such as absorbed dose, dose rate, monomer concentration and filter paper thickness on the grafting yield was studied. It was found that the degree of grafting increases with increasing absorbed

A. M. Dessouki; M. El-Tahawy; H. El-Boohy; S. A. El-Mongy; S. M. Badawy

1999-01-01

11

Chemical reactive filter paper prepared by radiation-induced graft polymerization-I  

Microsoft Academic Search

Chelating filter papers with chemically bonded amidoxime groups were synthesized by radiation-induced grafting of acrylonitrile onto filter paper (W3) followed by chemical treatment with hydroxylamine. The effect of grafting conditions such as absorbed dose, dose rate, monomer concentration and filter paper thickness on the grafting yield was studied. It was found that the degree of grafting increases with increasing absorbed

A. M. Dessouki; M. El-Tahawy; H. El-Boohy; S. A. El-Mongy; S. M. Badawy

1999-01-01

12

Cost Estimation of Butadiene-Grafted Polyvinyl Chloride Produced by Gas Phase Radiation-Induced Graft Polymerization.  

National Technical Information Service (NTIS)

Butadiene gas in contact with polyvinyl chloride (PVC) powder is easily graft-polymerized onto PVC by Co-60 gamma irradiation. The product polymer has a high impact strength comparable with that of blended PVC and a modifier (ABS, MBS, chlorinated polyeth...

K. Yoshida K. Araki

1976-01-01

13

Characterization of N-isopropyl acrylamide/acrylic acid grafted polypropylene nonwoven fabric developed by radiation-induced graft polymerization  

NASA Astrophysics Data System (ADS)

Radiation-induced graft copolymerization of N-isopropylacrylamide (NIPAAm) and acrylic acid (AA) mixture was carried out on polypropylene nonwoven fabric to develop a thermosensitive material and has been found to affect the thermal and physical characteristics of fabric. The grafted fabrics with different monomer ratios were characterized by thermal gravimetric analysis (TGA), fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), contact angle and atomic force microscopy (AFM). Results of FTIR clearly indicated that poly(acrylic acid) and poly(N-isopropyl acrylamide) were successfully grafted onto the membrane surface. TGA results showed that the thermal stability of PP fabric increased after grafting of NIPAAm/AA. The crystallinity values from DSC and XRD were found to decrease with increase in degree of grafting because of the addition of grafted chains within the noncrystalline region. The decrease in contact angles of the grafted fabric with an increase of the degree of grafting shows that PNIPAAm/PAA exists as the hydrophilic component. The increase in surface roughness after grafting was observed by AFM.

Kumari, Mamta; Gupta, Bhuvanesh; Ikram, Saiqa

2012-11-01

14

The role of hydroperoxides as a precursor in the radiation-induced graft polymerization of methyl methacrylate to ultra-high molecular weight polyethylene  

NASA Astrophysics Data System (ADS)

A graft polymerization of methyl methacrylate (MMA) to ultra-high molecular weight polyethylene (UHMWPE) with Co-60 ?-ray irradiation in air at room temperature has been carried out. The grafting yields were measured as a function of the storage time (elapsed time from the end of irradiation to the start of grafting), and it was found that the yields reach at the maximum values at around several days since the end of irradiation. In order to clarify the precursor of the graft polymerization, changes of the radical yields and the carbonyl groups were measured as a function of storage time with ESR and microscopic FT-IR, respectively. From the similarities between the depth profiles of the hydroperoxide formation and the grafting products, it was concluded that the hydroperoxides can be main precursors of the grafting of the radiation-induced polymerization of MMA to UHMWPE under the given conditions.

Enomoto, Ichiro; Katsumura, Yosuke; Kudo, Hisaaki; Sekiguchi, Masayuki

2010-06-01

15

Radiation-induced grafting polymerization of MMA onto polybutadiene rubber latex  

NASA Astrophysics Data System (ADS)

The grafting of methyl methacrylate (MMA) onto polybutadiene rubber latex by the direct radiation method was carried out. The effects of monomer concentration, absorbed dose and dose rate of gamma rays on the grafting yield were investigated. The graft copolymers were characterized by transmission electron microscopy (TEM), FTIR spectroscopy, and differential scanning calorimetry. TEM photographs revealed that the core-shell structures of latex particles are formed at low MMA content, and with the increasing of MMA content, the semi-IPN-like structure with core-shell could be developed due to the high gel fraction of polybutadiene (PBD) seed particles. In addition, infrared analysis confirmed that MMA could be grafted onto PBD molecular chains effectively under appropriate irradiation conditions. The interfacial adhesion between PBD rubber (core) and PMMA (shell) phases could be enhanced with the increase of MMA concentration.

Peng, Jing; Wang, Maolin; Qiao, Jinliang; Wei, Genshuan

2005-04-01

16

Thermosensitive membranes by radiation-induced graft polymerization of N-isopropyl acrylamide/acrylic acid on polypropylene nonwoven fabric  

NASA Astrophysics Data System (ADS)

Radiation-induced graft copolymerization of N-isopropylacrylamide (NIPAAm) and acrylic acid (AA) mixture was investigated on polypropylene nonwoven fabric to develop a thermosensitive material. The grafting was carried out using methanol, acetone and butanone as homopolymerization inhibitor in the reaction medium. Butanone was observed to give the maximum grafting. It was observed that the grafting is significantly influenced by the reaction conditions, such as radiation dose, monomer concentration, monomer ratio, solvent composition and reaction temperature. The degree of grafting increased as the AA and NIPAAm concentration in the reaction medium increased. The degree of grafting increased as the AA fraction in the NIPAAm/AA mixture increased. The temperature dependence of the grafting process is very much governed by the thermosensitive nature of the grafted chains right from the stage when initial grafting has taken place.

Ikram, Saiqa; Kumari, Mamta; Gupta, Bhuvanesh

2011-01-01

17

One-step functionalization of multi-walled carbon nanotubes by radiation-induced graft polymerization and their application as enzyme-free biosensors  

NASA Astrophysics Data System (ADS)

This paper describes the functionalization of multi-walled carbon nanotubes (MWNTs) by radiation-induced graft polymerization (RIGP) of vinyl monomers with functional groups and the application of these MWNTs in enzyme-free biosensors. The vinyl monomers used were acrylic acid (AAc), methacrylic acid (MAc), glycidyl methacrylate (GMA), maleic anhydride (MAn), and 4-vinylphenylboronic acid (VPBAc). Tubular-type MWNTs were obtained via RIGP of various vinyl monomers. The poly(VPBAc)-grafted MWNTs (PVBAc-g-MWNTs) were used as sensing sites in enzyme-free glucose sensors for the detection of glucose without enzymes. The PVBAc-g-MWNTs electrode displayed an excellent linear response to glucose concentration in the range 1.0-10 mM. The functionalized MWNTs prepared by RIGP can be used as biosensor materials.

Yang, Dae-Soo; Jung, Da-Jung; Choi, Seong-Ho

2010-04-01

18

RADIATION POLYMERIZATION DOSIMETRY  

Microsoft Academic Search

Quantitative studies of the high energy radiation photo sensitivity of ; certain liquid monomer-polymers have indicated a possible solution to the problem ; of high level dosimetry. Investigations of the relation between absorbed dose ; and factors which influence sensitivity have led to the development of a ; dependable system of radiation polymerization dosimetry. Changes in the ; composition of

F. E. Hoecker; I. W. Watkins; J. T. Han

1958-01-01

19

Electron-beam induced RAFT-graft polymerization of poly(acrylic acid) onto PVDF  

NASA Astrophysics Data System (ADS)

This paper explores for the first time the post-radiation-induced-graft polymerization on solid substrate using reversible addition-fragmentation transfer (RAFT) mechanism. Radiation-induced graft polymerization onto polymers is a potentially interesting technique to create easily new materials from highly resistant polymers, e.g. surface graft polymerization of acrylic acid (AA) onto poly(vinylidene difluoride) (PVDF) improves its surface properties without losing its excellent mechanical properties. As a consequence of the radical nature of the polymerization processes it is difficult to control molecular weight of grafted chains, and therefore design and standardize the properties of the final product. RAFT polymerization is a suitable method to obtain monodisperse polymers. The ability of the RAFT agents to control the polymer chain length could be an interesting approach to improve the grafted polymers obtained by post-radiation-induced-graft polymerization technique. In this way, graft polymerization of AA onto electron-beam irradiated ?-PVDF was performed using trithiocarbonic acid bis(1-phenylethyl) ester as a RAFT agent to control the radical polymerization. We studied several grafting parameters such as solvent, monomer concentration and grafting time in order to achieve a poly(acrylic acid) (PAA) layer onto PVDF surface. Acetic acid was found to be the best solvent for many reasons, as to drive graft polymerization mainly to the polymer surface, complete solubility and stability of all reactants. Hydrolysis of PAA chains was also studied in order to remove the trithiocarbonate functionality from the grafted polymer. A mild chemical condition was achieved in order to have thiol groups that were detected onto the modified PVDF by specific enzymatic reaction.

Grasselli, M.; Betz, N.

2005-07-01

20

Immobilization of an esterase inhibitor on a porous hollow-fiber membrane by radiation-induced graft polymerization for developing a diagnostic tool for feline kidney diseases.  

PubMed

Removal of the major urinary protein, cauxin, a carboxylesterase, from cat urine is essential for distinguishing between physiological and abnormal proteinuria by a urine dipstick. We have previously developed a material for removing cauxin by using lens culinaris agglutinin (LCA) lectin which targets the N-linked oligosaccharides present in cauxin. To improve the affinity and specificity toward cauxin, we immobilized 1,1,1-trifluoro-3-(2-sulfanylethylsulfanyl) propane-2-one, an inhibitor of esterases, to a polymer chain grafted on to a porous hollow-fiber membrane by applying radiation-induced graft polymerization. Normal male urine was forced to permeate through the pores rimmed by the ligand-immobilized polymer chain. Cauxin could not be detected in the effluent from the membrane. The residence time of the urine across a membrane thickness of 1 mm was set at 7 s. The respective dynamic and equilibrium binding capacities of the membrane for cauxin were 2 and 3 mg/g. The developed cauxin-affinity membrane material was more effective for diagnosing cat kidney diseases than the LCA lectin tip. PMID:24096669

Matsuno, Shinya; Umeno, Daisuke; Miyazaki, Masao; Suzuta, Yasuyuki; Saito, Kyoichi; Yamashita, Tetsuro

2013-10-07

21

Removal of phosphate using copper-loaded polymeric ligand exchanger prepared by radiation grafting of polypropylene/polyethylene (PP/PE) nonwoven fabric  

NASA Astrophysics Data System (ADS)

A novel polymeric ligand exchanger (PLE) was prepared for the removal of phosphate ions from water. 2,2?-dipyridylamine (DPA), a bidentate ligand forming compound with high coordination capacity with a variety of metal ions was bound to glycidyl methacrylate (GMA) grafted polypropylene/polyethylene (PP/PE) nonwoven fabric synthesized by radiation-induced grafting technique. DPA attachment on epoxy ring of GMA units was tested in different solvents, i.e. methanol, ethanol, dioxane and dimethylsulfoxide (DMSO). The highest amount of modification was achieved in dioxane. In order to prepare the corresponding PLE for the removal of phosphate, DPA-immobilized fabric was loaded with Cu(II) ions. Phosphate adsorption experiments were performed in batch mode at different pH (5-9) and phosphate concentrations. The fabric was found to be effective for the removal of phosphate ions. At every stage of preparation and use, the nonwoven fabric was characterized by thermal (i.e. DSC and TGA) and spectroscopic (FTIR) methods. Competitive adsorption experiments were also carried out using two solutions with different concentration levels at pH 7 to see the effect of competing ions. Phosphate adsorption was found to be effective and selective from solutions having trace amounts of competitive anions. It is expected that the novel PLE synthesized can be used for the removal of phosphate ions in low concentrations over a large range of pH.

Barsbay, Murat; Kavakl?, P?nar Akka?; Güven, Olgun

2010-03-01

22

Functional polymeric microspheres synthesized by radiation polymerization  

NASA Astrophysics Data System (ADS)

New functional microspheres consisting of diethylene glycol dimethacrylate (2G) and a methacryloyl monomer containing four amino acids, L-asparagynyl-L-alanyl-L-asparagynyl-L-proline methyl ester (MA-NANPOMe) were synthesized by radiation induced co-polymerization. These four amino acids were previously identified as a part of the immunodominant region of the circumsporozoite (CS) protein of Plasmodium falciparum. The use of this synthetic peptide as an antigen in immunoassay for malaria is promising: the microspheres exposed to the sera of malaria patients showed marked fluorescence, while the spheres contacted with sera of healthy donors showed no fluorescence.

Safranj, Agneza; Kano, Shigeyuki; Yoshida, Masaru; Omichi, Hideki; Katakai, Ryoichi; Suzuki, Mamoru

1995-08-01

23

Synthesis of Polymer Grafted Magnetite Nanoparticle with the Highest Grafting Density via Controlled Radical Polymerization  

NASA Astrophysics Data System (ADS)

The surface-initiated ATRP of benzyl methacrylate, methyl methacrylate, and styrene from magnetite nanoparticle is investigated, without the use of sacrificial (free) initiator in solution. It is observed that the grafting density obtained is related to the polymerization kinetics, being higher for faster polymerizing monomer. The grafting density was found to be nearly 2 chains/nm2 for the rapidly polymerizing benzyl methacrylate. In contrast, for the less rapidly polymerizing styrene, the grafting density was found to be nearly 0.7 chain/nm2. It is hypothesized that this could be due to the relative rates of surface-initiated polymerization versus conformational mobility of polymer chains anchored by one end to the surface. An amphiphilic diblock polymer based on 2-hydroxylethyl methacrylate is synthesized from the polystyrene monolayer. The homopolymer and block copolymer grafted MNs form stable dispersions in various solvents. In order to evaluate molecular weight of the polymer that was grafted on to the surface of the nanoparticles, it was degrafted suitably and subjected to gel permeation chromatography analysis. Thermogravimetric analysis, transmission electron microscopy, and Fourier transform infrared spectroscopy were used to confirm the grafting reaction.

Babu, Kothandapani; Dhamodharan, Raghavachari

2009-09-01

24

Radiation-hardened polymeric films  

DOEpatents

The radiation-induced conductivity of polymeric dielectrics with low electronic mobility is reduced by doping with electron donor or electron acceptor compounds at a level of 10/sup 15/ to 10/sup 21/ molecules of dopant/cm/sup 3/. Polyesters, polyolefins, perfluoropolyolefins, vinyl polymers, vinylidene polymers, polycarbonates, polysulfones and polyimides can benefit from such a treatment. Usable dopants include 2,4,7-trinitro-9-fluorenone, tetracyanethylene, 7,7,8,8-tetracyanoquinodimethane, m-dinitrobenzene, 2-isopropylcarbazole, and triphenylamine.

Arnold, C. Jr.; Hughes, R.C.; Kepler, R.G.; Kurtz, S.R.

1984-07-16

25

Radiation-hardened polymeric films  

DOEpatents

The radiation-induced conductivity of polymeric dielectrics with low electronic mobility is reduced by doping with electron donor or electron acceptor compounds at a level of 10.sup.15 to 10.sup.21 molecules of dopant/cm.sup.3. Polyesters, polyolefins, perfluoropolyolefins, vinyl polymers, vinylidene polymers, polycarbonates, polysulfones and polyimides can benefit from such a treatment. Usable dopants include 2,4,7-trinitro-9-fluorenone, tetracyanethylene, 7,7,8,8-tetracyanoquinodimethane, m-dinitrobenzene, 2-isopropylcarbazole, and triphenylamine.

Arnold, Jr., Charles (Albuquerque, NM); Hughes, Robert C. (Albuquerque, NM); Kepler, R. Glen (Albuquerque, NM); Kurtz, Steven R. (Albuquerque, NM)

1986-01-01

26

Emulsion graft polymerization of 4-chloromethylstyrene on kenaf fiber by pre-irradiation method  

NASA Astrophysics Data System (ADS)

The stability of micelle size in 3% 4-chloromethylstyrene (CMS), 0.3% Tween 20 in water emulsion over time was studied using a static light scattering. It was found that the micelle diameter decreased with storage time and temperature. The influence of micelle size over time was then explored by adjusting the ratio of CMS to Tween 20 (10:1, 10:2, 10:4) at CMS concentration of 0.2-5.0%. It was found that the increase in average micelle diameter resulted in a decreased in the stability of CMS emulsion. Graft polymerization of CMS on kenaf fiber was carried out in emulsion with 350 nm micelle at various CMS concentrations at a dose of 150 kGy. It was found that the degree of grafting (Dg) was strongly dependent on the monomer concentration and time. However, the increase in micelles diameter from 250 nm to 500 nm resulted in the increased in Dg from 3% to 153%. This extraordinary result led us to investigate the micelle size distributions of CMS emulsion during graft polymerization. It was found that the diameter of micelle decreased rapidly to 100 nm within 2 h. It was discovered from digital photomicrography the existence of multiple emulsions in the CMS emulsion. It was proposed that the enhancement of grafting yield is governed by emulsion breakdown mechanisms through radical effect during radiation induced graft polymerization.

Mohamed, Nor Hasimah; Tamada, Masao; Ueki, Yuji; Seko, Noriaki

2013-01-01

27

Radiation and Ozone Initiated Graft Copolymerization.  

National Technical Information Service (NTIS)

Radiation and ozone initiated graft copolymerization reactions were investigated for the synthesis of new technologically useful elastomers. Significant grafting was observed for many of the various combinations of monomers and polymers investigated. Radi...

J. W. McGarvey

1964-01-01

28

Radiation-induced graft polymerization and sulfonation of glycidyl methacrylate on to porous hollow-fiber membranes with different pore sizes  

NASA Astrophysics Data System (ADS)

An epoxy group containing monomer, glycidyl methacrylate, was grafted on to a porous hollow-fiber membrane, made of polyethylene, whose different pore sizes ranged from 0.2 to 0.5 ?m. The resulting epoxy group was converted into a sulfonic acid group as a cation-exchange group to capture metal ions. The porous network was retained after grafting and subsequent sulfonation because the poly-GMA chains invaded the polymer matrix. An increase in the SO3H group density of the graft chain decreased the permeability of pure water because the graft chains expanded toward the pore interior due to their mutual electrostatic repulsion. The ion-exchange adsorption of Pb ions during the permeation of a Pb(NO3)2 solution through the pores edged by the cation-exchange graft chains was observed with a negligible diffusional mass-transfer resistance.

Kim, M.; Saito, K.

2000-02-01

29

Synthesis of antibacterial cotton fabric by radiation-induced grafting of [2-(Methacryloyloxy)ethyl]trimethylammonium chloride (MAETC) onto cotton  

Microsoft Academic Search

Gamma radiation has been used to covalently link polymer chains of [2-(Methacryloyloxy)ethyl]trimethylammonium chloride (MAETC) to cotton fabric by mutual radiation grafting. The grafted samples have been characterized for water uptake, surface morphology and thermal stability. Grafting extent was found to increase with the dose and monomer concentration. However high dose rate, O2, inorganic salts and alcohols suppressed grafting. Radiation polymerized

N. K. Goel; M. S. Rao; Virendra Kumar; Y. K. Bhardwaj; C. V. Chaudhari; K. A. Dubey; S. Sabharwal

2009-01-01

30

Enhancing oil-sorption performance of polypropylene fiber by surface modification via UV-induced graft polymerization of butyl acrylate.  

PubMed

In order to improve oil sorption performances, polypropylene (PP) fiber was modified through graft polymerization with butyl acrylate (BA) initiated by ultraviolet (UV) radiation in isopropanol/water mixture solution. Fourier transform infrared (FT-IR) spectra, scanning electron microscopy (SEM) and specific surface area were used to characterize the chemical and morphological changes of the PP fiber surface. Static contact angle (CA) measurements showed that the hydrophilicity of original PP fiber was enhanced after graft polymerization. The grafted fiber exhibited an excellent oil-sorption, oil-retention performance, fast saturation-sorption rate and superior reusability of oil. When the grafting degree was 15.55%, the maximum oil-sorption capacity reached 18.35 g/g, while the oil-sorption capacity of original PP fiber was only 11.54 g/g. After the tenth cycle of reuse, the grafted fiber sorbent assembly only lost 30% of its virgin sorption capacity. PMID:23109581

Li, Shaoning; Wei, Junfu; Wang, Ao; Nie, Yuexia; Yang, Hang; Wang, Lei; Zhou, Bin

2012-01-01

31

Pre-irradiation induced emulsion graft polymerization of acrylonitrile onto polyethylene nonwoven fabric  

NASA Astrophysics Data System (ADS)

Acrylonitrile has been widely used in the modification of polymers by graft polymerization. In the present work, pre-irradiation induced emulsion graft polymerization method is used to introduce acrylonitrile onto PE nonwoven fabric instead of the traditional reaction in organic solvents system. The degree of grafting (DG) is measured by gravimetric method and the kinetics of the graft polymerization is studied. The existence of the graft chains is proven by Fourier transform infrared spectroscopy (FT-IR) analysis. Thermal stability of the grafted polymer is measured by Thermogravimetric analysis (TGA).

Liu, Hanzhou; Yu, Ming; Deng, Bo; Li, Linfan; Jiang, Haiqing; Li, Jingye

2012-01-01

32

Synthesis and characterization of poly(phenylene oxide) graft copolymers by atom transfer radical polymerizations  

Microsoft Academic Search

A series of comb-like poly(phenylene oxide)s (PPO) graft copolymers with controlled grafting density and length of grafts were synthesized by atom transfer radical polymerization (ATRP). The ?-bromo-poly(2,6-dimethyl-1,4-phenylene oxide)s (BPPO) were used as macroinitiators to polymerize vinyl monomers and the graft copolymers carrying polystyrene (PS), poly(p-acetoxystyrene) (PAS), and poly(methyl methacrylate) (PMMA) as side chains were synthesized and characterized by NMR, FTIR,

Mong Liang; Yong-Jhao Jhuang; Chun-Fu Zhang; Wei-Jhuan Tsai; Hui-Chuan Feng

2009-01-01

33

Biodegradable metal adsorbent synthesized by graft polymerization onto nonwoven cotton fabric  

NASA Astrophysics Data System (ADS)

A fibrous adsorbent for Hg ions was synthesized by radiation-induced emulsion graft polymerization of glycidyl methacrylate (GMA) onto a nonwoven cotton fabric and subsequent chemical modification. The optimal pre-irradiation dose for initiation of the graft polymerization of GMA, which minimized the effects of radiation damage on the mechanical strength of the nonwoven cotton fabric, was found to be 10 kGy. The GMA-grafted nonwoven cotton fabric was subsequently modified with ethylenediamine (EDA) or diethylenetriamine (DETA) to obtain a Hg adsorbent. The resulting amine-type adsorbents were evaluated for batch and continuous adsorption of Hg. In batch adsorption, the distribution coefficients of Hg reached 1.9×105 and 1.0×105 for EDA- and DETA-type adsorbents, respectively. A column packed with EDA-type adsorbent removed Hg from 1.8 ppm Hg solution at a space velocity of 100 h-1, which corresponds to 16,000 times the volume of the packed adsorbent. The adsorbed Hg on the EDA-type adsorbent could be completely eluted by 1 M HCl solution. A microbial oxidative degradation test revealed that the EDA-type adsorbent is biodegradable.

Sekine, Ayako; Seko, Noriaki; Tamada, Masao; Suzuki, Yoshio

2010-01-01

34

Radiation grafting of methyl methacrylate monomer on natural rubber latex. [Gamma radiation  

SciTech Connect

A method of radiation grafting of methyl methacrylate (MMA) monomer on natural rubber (NR) latex has been studied. The irradiation dose in radiation emulsion polymerization of MMA monomer was lower compared to the irradiation dose for grafting of MMA monomer on NR latex, in order to obtain the same degree of conversion. This is due to the size of the rubber particles which are quite large and, hence, not sufficient to ensure an ideal emulsion polymerization. The irradiation dose for radiation grafting of MMA monomer on latex was around 300 krad to obtain a 75% degree of conversion. However, this irradiation dose was lower compared to the irradiation dose for bulk polymerization of MMA momomer, in order to obtain the same degree of conversion. This is due to the gel effect in the viscous media. Radiation grafting of MMA monomer on NR latex does not influence the pH of the latex, but influences the viscosity significantly. The viscosity of the NR latex increased with an increase in irradiation dose, due to the increase of the total solid content in the latex. The MMA monomer converted to P-MMA in NR latex was largely grafted on the NR, or at least insoluble in a solvent for P-MMA, such as acetone or toluene. The hardness of the pure gum vulcanizate increased with an increase in the degree of grafting or P-MMA content, but the other physical properties, such as tensile strength, modulus, elongation at break, and thermal stability, were not greatly influenced by the degree of grafting. 9 references, 3 figures, 5 tables.

Sundardi, F.; Kadariah, S.

1984-05-01

35

Inorganic surface nanostructuring by atmospheric pressure plasma-induced graft polymerization.  

PubMed

Surface graft polymerization of 1-vinyl-2-pyrrolidone onto a silicon surface was accomplished by atmospheric pressure (AP) hydrogen plasma surface activation followed by graft polymerization in both N-methyl-2-pyrrolidone (NMP) and in an NMP/water solvent mixture. The formation of initiation sites was controlled by the plasma exposure period, radio frequency (rf) power, and adsorbed surface water. The surface number density of active sites was critically dependent on the presence of adsorbed surface water with a maximum observed at approximately a monolayer surface water coverage. The surface topology and morphology of the grafted polymer layer depended on the solvent mixture composition, initial monomer concentration, reaction temperature, and reaction time. Grafted polymer surfaces prepared in pure NMP resulted in a polymer feature spacing of as low as 5-10 nm (average feature diameter of about 17 nm), an rms surface roughness range of 0.18-0.72 nm, and a maximum grafted polymer layer thickness of 5.5 nm. Graft polymerization in an NMP/water solvent mixture, however, resulted in polymer feature sizes that increased up to a maximum average feature diameter of about 90 nm at [NMP] = 60% (v/v) with polymer feature spacing in the range of 10-50 nm. The surface topology of the polymer-modified silicon surfaces grafted in an NMP/water solvent mixture exhibited a bimodal feature height distribution. In constrast, graft polymerization in pure NMP resulted in a narrow feature height distribution of smaller-diameter surface features with smaller surface spacing. The results demonstrated that, with the present approach, the topology of the grafted polymer surface was tunable by adjusting the NMP/water ratio. The present surface graft polymerization method, which is carried out under AP conditions, is particularly advantageous for polymer surface structuring via radical polymerization and can, in principle, be scaled to large surfaces. PMID:17824715

Lewis, Gregory T; Nowling, Gregory R; Hicks, Robert F; Cohen, Yoram

2007-09-08

36

Synthesis of antibacterial cotton fabric by radiation-induced grafting of [2-(Methacryloyloxy)ethyl]trimethylammonium chloride (MAETC) onto cotton  

NASA Astrophysics Data System (ADS)

Gamma radiation has been used to covalently link polymer chains of [2-(Methacryloyloxy)ethyl]trimethylammonium chloride (MAETC) to cotton fabric by mutual radiation grafting. The grafted samples have been characterized for water uptake, surface morphology and thermal stability. Grafting extent was found to increase with the dose and monomer concentration. However high dose rate, O2, inorganic salts and alcohols suppressed grafting. Radiation polymerized poly(MAETC) and MAETC-g-cotton samples were tested for their antibacterial efficacy against various bacteria and were found to possess significant antibacterial activity.

Goel, N. K.; Rao, M. S.; Kumar, Virendra; Bhardwaj, Y. K.; Chaudhari, C. V.; Dubey, K. A.; Sabharwal, S.

2009-06-01

37

Radiation sterilization of polymeric implant materials  

SciTech Connect

High-energy irradiation sterilization of medical devices and implants composed of polymeric biomaterials that are in contact with tissue and/or blood, may adversely affect their long-term mechanical and/or biological performance (tissue and/or blood compatibility). Since many polymeric implants may contain trace quantities of catalysts and/or other additives, the effect of high-energy radiation on these additives, and possible synergistic effects with the polymer chains under the influence of high-energy radiation, must be considered. It is essential to indicate whether polymeric implants are used in short-term (acute) or long-term (chronic) applications. Relatively small changes in their physicochemical, mechanical, and biological properties may be tolerable in the short term, whereas similar changes may lead to catastrophic failures in long-term applications. Therefore, polymeric implants which are to be sterilized by high-energy irradiation should be carefully evaluated for long-term property changes which may be induced by the radiation.

Bruck, S.D.; Mueller, E.P.

1988-08-01

38

Surface modification of ultra high molecular weight polyethylene fibers via the sequential photoinduced graft polymerization  

NASA Astrophysics Data System (ADS)

In this study, a sequential photoinduced graft polymerization process was proposed to improve the poor interfacial bonding property of ultra high molecular weight polyethylene (UHMWPE) fibers. The polymerization was initiated by dormant semipinacol (SP) groups and carried out in a thin liquid layer. Methacrylic acid (MAA) and acryl amide (AM) were grafted stepwise onto the surface of UHMWPE fibers. Attenuated total reflectance infrared spectroscopy (ATR-IR) and thermo gravimetric analysis (TGA) confirmed the grafting. The analysis result of pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) indicated the structure of grafted chains. Scanning electron microscopy (SEM) images and atomic force microscopy (AFM) images revealed the apparent morphology changing, and the grafted layers were observed. Interfacial shear stress (IFSS) test of the modified fibers showed an extensively improved interfacial bonding property. The active groups grafted onto the fibers would supply enough anchor points for the chemical bonding with various resins or further reactions.

Li, Zhi; Zhang, Wei; Wang, Xinwei; Mai, Yongyi; Zhang, Yumei

2011-06-01

39

Synthesis of polymer grafted carbon nanotubes by nitroxide mediated radical polymerization in the presence of spin-labeled carbon nanotubes  

Microsoft Academic Search

Multiwalled carbon nanotubes (MWCNT) were grafted with polystyrene by in situ nitroxide mediated radical polymerization in the presence of TEMPO (2,2,6,6-tetramethylpiperidinyl-1-oxyl) functionalized MWCNT, which was synthesized by the reaction between 4-hydroxyl-TEMPO (HO–TEMPO) and carbonyl chloride groups on the MWCNT. Although the controllability of the polymerization was not high, highly soluble grafted MWCNTs were indeed obtained, indicating that the graft polymerization

De-Qin Fan; Jun-Po He; Wei Tang; Jiang-Tao Xu; Yu-Liang Yang

2007-01-01

40

MMA/DVB emulsion surface graft polymerization initiated by UV light.  

PubMed

Methyl methacrylate/1,2-divinylbenzene (MMA/DVB) in an opaque emulsion were successfully grafted onto the surface of polymeric substrate under the irradiation of UV light with benzophenone (BP) as a photoinitiator that was previously coated on the substrate surface. Monomer conversion, grafting efficiency, and grafting yields were determined by the gravimetric method. ATR-IR, AFM, and TEM were used to characterize the surface composition, to observe the topography of the grafted substrates, and to view inter-film colloid particles formed by cross-linking. The results reveal that, with the opaque MMA/DVB emulsion system and CPP film as substrate, the monomer conversion is in the range of 15-55%, the grafting efficiency is about 80%, the grafting yield reaches 5%, and the thickness of the graft layer can be controlled in the range 0.09-1.5 microm. Images of AFM show that the graft layer is piled up by nanoparticles (about 30-50 nm in diameter), which are linked together and tied to the substrate surface with covalent bonds. A possible model of surface graft polymerization including surface initiating, nucleation, and shish kebab growing is put forward to interpreting the above results. PMID:15248706

Wang, Yongxin; Yang, Wantai

2004-07-20

41

Radiation-induced grafting of dimethylaminoethylmethacrylate onto PE/PP nonwoven fabric  

NASA Astrophysics Data System (ADS)

A new adsorbent was prepared by radiation-induced graft polymerization of dimethylaminoethylmethacrylate (DMAEMA) onto polyethylene/polypropylene (PE/PP) nonwoven fabric. The trunk polymer was irradiated by electron beam at a voltage of 2 MeV and a current of 3 mA in nitrogen atmosphere at dry-ice temperature to different doses. The degree of grafting was determined as a function of irradiation dose, monomer concentration, temperature and reaction time. Grafting conditions were optimized and about 150% grafted samples were used for further experiments. DMAEMA grafted polymer was later protonated in acid solution to prepare specialty adsorbent for the removal of phosphate. Adsorption experiments were performed in column mode for removal of phosphate. It was shown that 2000 bed volumes of phosphate-free water can be produced from 100 ppb phosphate (as P) solution at high space velocity.

Kavakl?, P?nar Akka?; Kavakl?, Cengiz; Seko, Noriaki; Tamada, Masao; Güven, Olgun

2007-12-01

42

Surface-initiated graft polymerization on multiwalled carbon nanotubes pretreated by corona discharge at atmospheric pressure.  

PubMed

Surface-initiated graft polymerization on multi-walled carbon nanotubes pretreated with a corona discharge at atmospheric pressure was explored. The mechanism of the corona-discharge-induced graft polymerization is discussed. The results indicate that MWCNTs were encapsulated by poly(glycidyl methacrylate) (PGMA), demonstrating the formation of PGMA-grafted MWCNTs (PGMA-g-MWCNTs), with a grafting ratio of about 22 wt%. The solubility of PGMA-g-MWCNTs in ethanol was dramatically improved compared to pristine MWCNTs, which could contribute to fabricating high-performance polymer/MWCNTs nanocomposites in the future. Compared with most plasma processes, which operate at low pressures, corona discharge has the merit of working at atmospheric pressure. PMID:20644821

Xu, Lihua; Fang, Zhengping; Song, Ping'an; Peng, Mao

2009-11-24

43

Comparison of surface modifications of poly(ether urethanes) by chemical infusion and graft polymerization  

SciTech Connect

Our approach to surface modification uses the chemical infusion process to introduce materials into the outermost layer of the polymeric material, thereby altering the surface without changing the bulk properties of the polymer. The infused materials may slowly diffuse out of the infusion layer if they are volatile or highly mobile. However, if polymeric infusant materials are employed, they may become chain entangled with the host polymer and result in a permanently modified surface. A second approach utilizes photo-initiated graft polymerization of poly(ether urethanes) with an appropriate monomer. We have explored both of these methods by examining the infusion of polyvinylpyrrolidone (PVP) and poly(ethylene glycol) (PEG) into commercially available poly(ether urethanes) and the graft polymerization of N-vinyl pyrrolidone onto poly(ether urethanes). Results are presented here. 7 refs., 1 tab.

Wrobleski, D.A.; Cash, D.L.; Hermes, R.E.

1988-01-01

44

Biomimetic phosphorylcholine polymer grafting from polydimethylsiloxane surface using photo-induced polymerization  

Microsoft Academic Search

The biomimetic synthetic phospholipid polymer containing a phosphorylcholine group, 2-methacryloyloxyethyl phosphorylcholine (MPC), has improved the surface property of biomaterials. Both hydrophilic and anti-biofouling surfaces were prepared on polydimethylsiloxane (PDMS) with MPC grafted by surface-initiated photo-induced radical polymerization. Benzophenone was used as the photoinitiator. The quantity of the adsorbed initiator on PDMS was determined by UV absorption and ellipsometry. The poly(MPC)-grafted

Tatsuro Goda; Tomohiro Konno; Madoka Takai; Toru Moro; Kazuhiko Ishihara

2006-01-01

45

Graft polymerization of vinyl monomers onto cotton fibres pretreated with amines  

Microsoft Academic Search

The influence of treating cotton fibres with several amines on the mechanical properties, moisture sorption ability before\\u000a and after graft polymerization, and on graft yields for various water-soluble and water-insoluble vinyl monomers were analysed.\\u000a As compared to water, the treatment with amines, ethylenediamine (EDA) in particular, resulted in a decrease in the crystallinity\\u000a and tensile strength of the cotton fibres,

Yasumitsu Uraki; Makoto Ubukata; Koki Itoyama

2008-01-01

46

POLYMERIZATION OF VINYL CHLORIDE UNDER EFFECT OF $gamma$RADIATION  

Microsoft Academic Search

Experiments were conducted on the polymerization of technical vinyl ; chloride under the effect of gamma radiation at with an activity of 18,000 g-; equiv Ra was used as the source. Ths polymerization kinetics was shown to obey ; the general laws governing free radical polymerization. There is a considerable ; induction period, because the initial radicals react with inhibiting

L. D. Bubis; V. L. Karpov; Yu. M. Malinskii; D. M. Yanovskii

1962-01-01

47

RADIATION-INDUCED POLYMERIZATION OF FORMALDEHYDE IN LIQUID STATE  

Microsoft Academic Search

Monomeric formaldehyde is rapidly polymerized by ionizing radiation, ; especially in the liquid state, and gives the polyoxymethylene of high molecular ; weight. The reaction rate itself is large but considerably different in bulk and ; solution systems. There is no linear relation between the polymerization rate ; and monomer concentration. This paper confirms these facts for solution ; polymerization

S. Nakashio; K. Takahashi; M. Kondo

1963-01-01

48

Functional polyolefins: poly(ethylene)-graft-poly(tert-butyl acrylate) via atom transfer radical polymerization from a polybrominated alkane.  

PubMed

Poly(cis-cyclooctene) is synthesized via ring-opening metathesis polymerization in the presence of a chain-transfer agent and quantitatively hydrobrominated. Subsequent graft polymerization of tert-butyl acrylate (tBA) via Cu-catalyzed atom transfer radical polymerization (ATRP) from the non-activated secondary alkyl bromide moieties finally results in PE-g-PtBA copolymer brushes. By varying the reaction conditions, a series of well-defined graft copolymers with different graft densities and graft lengths are prepared. The maximum extent of grafting in terms of bromoalkyl groups involved is approximately 80 mol%. DSC measurements on the obtained graft copolymers reveal a decrease in T(m) with increasing grafting density. PMID:22095785

Xu, Guangjuan; Wang, Dongren; Buchmeiser, Michael R

2011-11-18

49

Graft polymerization and plasma treatment of polymer membranes for fouling reduction: A review  

Microsoft Academic Search

This article presents a review of recent developments in surface modification of polymer membranes via graft polymerization and plasma treatment for reduction of fouling with organic compounds and microorganisms in pressure driven membrane processes. The factors affecting membrane fouling, such as membrane hydrophilicity, charge and surface roughness are discussed. The recent studies in which the reduction of organic fouling and

Victor M. Kochkodan; Virender K. Sharma

2012-01-01

50

Polysiloxane modified epoxy polymer networks—I. Graft interpenetrating polymeric networks  

Microsoft Academic Search

Graft interpenetrating polymeric networks of epoxy resin and polydimethylsiloxane (PDMS) were synthesized using 3-aminopropyltrimethoxysilane (?-APS) as coupling agent. The dynamic mechanical analysis shows partially mutual compatibility between these two thermodynamically immiscible polymers. Due to the inappropriate domain size and the poor cohesive properties between epoxy resin and PDMS domain, the fracture energy (GIC) decreased drastically at low PDMS content (5%).

Po-Hou Sung; Chien-Yang Lin

1997-01-01

51

A short review of radiation-induced raft-mediated graft copolymerization: A powerful combination for modifying the surface properties of polymers in a controlled manner  

NASA Astrophysics Data System (ADS)

Surface grafting of polymeric materials is attracting increasing attention as it enables the preparation of new materials from known and commercially available polymers having desirable bulk properties such as thermal stability, elasticity, permeability, etc., in conjunction with advantageous newly tailored surface properties such as biocompatibility, biomimicry, adhesion, etc. Ionizing radiation, particularly ? radiation is one of the most powerful tools for preparing graft copolymers as it generates radicals on most substrates. With the advent of living free-radical polymerization techniques, application of ? radiation has been extended to a new era of grafting; grafting in a controlled manner to achieve surfaces with tailored and well-defined properties. This report presents the current use of ? radiation in living free-radical polymerization and highlights the use of both techniques together as a combination to present an advance in the ability to prepare surfaces with desired, tunable and well-defined properties.

Barsbay, Murat; Güven, Olgun

2009-12-01

52

Argon Plasma-Induced Graft Polymerization of PEGMA on Chitosan Membrane Surface for Cell Adhesion Improvement  

NASA Astrophysics Data System (ADS)

For its biocompatibility and biodegradability, chitosan has had considerable attention for biomedical applications in recent years. In this paper, polymerization of poly (ethylene glycol) methyl ether methacrylate (PEGMA) was grafted onto chitosan membrane surface through argon plasma-induced graft polymerization. The surface properties after modification were characterized by contact angle measurement, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. The results indicated that PEGMA can be grafted successfully onto chitosan membrane surface. The surface hydrophilicity and free energy were improved and the surface roughness increased after modification. The adhesion of a human corneal epithelial cell (HCEC) on chitosan membrane surface was enhanced due to improvement of surface free energy and roughness.

Yin, Shiheng; Ren, Li; Wang, Yingjun

2013-10-01

53

The effects of early postoperative radiation on vascularized bone grafts  

SciTech Connect

The effects of early postoperative radiation were assessed in free nonvascularized and free vascularized rib grafts in the canine model. The mandibles of one-half of the dogs were exposed to a cobalt 60 radiation dose of 4080 cGy over a 4-week period, starting 2 weeks postoperatively. The patency of vascularized grafts was confirmed with bone scintigraphy. Histological studies, including ultraviolet microscopy with trifluorochrome labeling, and histomorphometric analyses were performed. Osteocytes persist within the cortex of the vascularized nonradiated grafts to a much greater extent than in nonvascularized, nonradiated grafts. Cortical osteocytes do not persist in either vascularized or nonvascularized grafts subjected to radiation. New bone formation is significantly retarded in radiated grafts compared with nonradiated grafts. Periosteum and endosteum remained viable in the radiated vascularized grafts, producing both bone union and increased bone turnover, neither of which were evident to any significant extent in nonvascularized grafts. Bone union was achieved in vascularized and non-vascularized nonradiated bone. In the radiated group of dogs, union was only seen in the vascularized bone grafts.

Evans, H.B.; Brown, S.; Hurst, L.N. (Division of Plastic and Reconstructive Surgery, University of Western Ontario, London (Canada))

1991-06-01

54

Aseptic Endotoxemia in Radiation Injury and Graft Versus Host Disease.  

National Technical Information Service (NTIS)

Endotoxemia of intestinal origin may impair physiologic and immunologic functions in individuals subjected to high doses of either ionizing radiation or radiation followed by transplants of foreign immune competent cells capable of producing graft versus ...

R. I. Walker G. D. Ledney C. B. Galley

1975-01-01

55

Antimicrobial hydantoin-grafted poly(?-caprolactone) by ring-opening polymerization and click chemistry.  

PubMed

Novel degradable and antibacterial polycaprolactone-based polymers are reported in this work. The polyesters with pendent propargyl groups are successfully prepared by ring-opening polymerization and subsequently used to graft antibacterial hydantoin moieties via click chemistry by a copper(I)-catalyzed azide-alkyne cycloaddition reaction. The well-controlled chemical structures of the grafted copolymers and its precursors are verified by FT-IR spectroscopy, NMR spectroscopy, and GPC characterizations. According to the DSC and XRD results, the polymorphisms of these grafted copolymers are mostly changed from semicrystalline to amorphous depending on the amount of grafted hydantoin. Antibacterial assays are carried out with Bacillus subtilis and two strains of Escherichia coli and show fast antibacterial action. PMID:23008215

Tan, Licheng; Maji, Samarendra; Mattheis, Claudia; Chen, Yiwang; Agarwal, Seema

2012-09-24

56

Enhanced Polymer Grafting from Multiwalled Carbon Nanotubes through Living Anionic Surface-Initiated Polymerization.  

SciTech Connect

Anionic surface-initiated polymerization of ethylene oxide and styrene has been performed using multiwalled carbon nanotubes (MWNTs) functionalized with anionic initiators. The surface of MWNTs was modified via covalent attachment of precursor anions such as 4-hydroxyethyl benzocyclobutene (BCBEO) and 1-benzocyclobutene-1 -phenylethylene (BCB-PE) through Diels-Alder cycloaddition at 235 C. Surface-functionalized MWNTs-g-(BCB-EO)n and MWNTs-g-(BCB-PE)n with 23 and 54 wt % precursor initiators, respectively, were used for the polymerizations. Alkoxide anion on the surface of MWNTs-g-(BCB-EO)n was generated through reaction with potassium triphenylmethane for the polymerization of ethylene oxide in tetrahydrofuran and phenyl substituted alkyllithium was generated from the surface of MWNTs-g-(BCB-PE)n using sec-butyllithium for the polymerization of styrene in benzene. In both cases, the initiation was found to be very slow because of the heterogeneous reaction medium. However, the MWNTs gradually dispersed in the reaction medium during the polymerization. A pale green color was noticed in the case of ethylene oxide polymerization and the color of initiator as well as the propagating anions was not discernible visually in styrene polymerization. Polymer grafted nanocomposites, MWNTs-g-(BCB-PEO)n and MWNTs-g-(BCB-PS)n containing a very high percentage of hairy polymer with a small fraction of MWNTs (<1 wt %) were obtained. The conversion of ethylene oxide and the weight percent of PEO on the surface of the MWNTs increased with increasing reaction time indicating a controlled polymerization. The polymer-grafted MWNTs were characterized using FTIR, 1H NMR, Raman spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and transmission electron microscopy (TEM). Size exclusion chromatography of the polymer grafted MWNTs revealed broad molecular weight distributions (1.3 < Mw/Mn < 1.8) indicating the presence of different sizes of polymer nanocomposites. The TEM images showed the presence of thick layers of polymer up to 30 nm around the MWNTs. The living nature of the growing polystyryllithium was used to produce diblock copolymer grafts using sequential polymerization of isoprene on the surface of MWNTs.

Sakellariou, Georgios [ORNL; Ji, Haining [ORNL; Mays, Jimmy [ORNL; Baskaran, Durairaj [University of Tennessee, Knoxville (UTK)

2008-01-01

57

Reduced platelets and bacteria adhesion on poly(ether ether ketone) by photoinduced and self-initiated graft polymerization of 2-methacryloyloxyethyl phosphorylcholine.  

PubMed

Aromatic poly(ether ether ketone) (PEEK) is a super engineering plastic, which has good mechanical properties and is resistant to physical and chemical stimuli. We have, therefore, attempted to use PEEK in cardiovascular devices. Synthetic cardiovascular devices require both high hemocompatibility and anti-inflammatory activity in addition to the mechanical properties. We modified the PEEK surface by photoinduced and self-initiated graft polymerization with 2-methacryloyloxyethyl phosphorylcholine (MPC; PMPC-grafted PEEK) for obtaining good antithrombogenicity. Polymerization was carried out on the surface of PEEK under radiation of ultraviolet (UV) light during which we controlled monomer concentrations, temperatures, and UV intensities. The biological performance of the PMPC-grafted PEEK was examined and compared with that of unmodified PEEK. With increase in the thickness of the PMPC layer, the amount of fibrinogen adsorption decreased significantly in comparison to that in the case of unmodified PEEK. When placed in contact with human platelet-rich plasma, surface of the PMPC-grafted PEEK clearly showed inhibition of platelet adhesion and activation. Also, bacterial adhesion was reduced dramatically on the PMPC-grafted PEEK. Thus, the PMPC grafting on PEEK improved the antithrombogenicity. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013. PMID:23720384

Tateishi, Takaharu; Kyomoto, Masayuki; Kakinoki, Sachiro; Yamaoka, Tetsuji; Ishihara, Kazuhiko

2013-05-29

58

Modeling of thermal and radiative aging of polymeric cable materials  

Microsoft Academic Search

It is of critical importance to safety in the nuclear power industry to estimate the lifetime of polymeric materials in an environment featuring elevated temperatures and radiation. To this end, the authors are examining the aging of polymeric materials, in cables and other components in nuclear reactor containments by comparing aging processes for a variety of materials under natural conditions

Montgomery T. Shaw; Yong-Ming Liu

1996-01-01

59

Plasma polymerized thin coating as a protective layer of carbon nanotubes grafted on carbon fibers  

NASA Astrophysics Data System (ADS)

Nanoparticles addition is widely studied to improve properties of carbon fiber reinforced composites. Here, hybrid carbon fiber results from grafting of carbon nanotubes (CNT) by Chemical Vapor Deposition (CVD) on the carbon fiber for mechanical reinforcement and conductive properties. Both tows and woven fabrics made of the hybrid fibers are added to the matrix for composite processing. However handling hybrid fibers may induce unwilling health risk due to eventual CNT release and a protective layer is required. A thin coating layer is deposited homogeneously by low pressure plasma polymerization of an organic monomer without modifying the morphology and the organization of grafted CNTs. The polymeric layer effect on the electrical behavior of hybrid fiber is assessed by conductivity measurements. Its influence on the mechanical properties is also studied regarding the interface adhesion between fiber and matrix. The protective role of layer is demonstrated by means of friction constraints applied to the hybrid fiber.

Einig, A.; Rumeau, P.; Desrousseaux, S.; Magga, Y.; Bai, J. B.

2013-04-01

60

Combining spontaneous polymerization and click reactions for the synthesis of polymer brushes: a "grafting onto" approach.  

PubMed

Two novel benzofulvene monomers bearing propargyl or allyl groups have been synthesized by means of readily accessible reactions, and were found to polymerize spontaneously by solvent removal, in the apparent absence of catalysts or initiators, to give the corresponding polybenzofulvene derivatives bearing clickable propargyl or allyl moieties. The clickable propargyl and allyl groups were exploited in appropriate click reactions to develop a powerful and versatile "grafting onto" synthetic methodology for obtaining tailored polymer brushes. PMID:23836403

Cappelli, Andrea; Grisci, Giorgio; Paolino, Marco; Castriconi, Federica; Giuliani, Germano; Donati, Alessandro; Lamponi, Stefania; Mendichi, Raniero; Boccia, Antonella Caterina; Samperi, Filippo; Battiato, Salvatore; Paccagnini, Eugenio; Gentile, Mariangela; Licciardi, Mariano; Giammona, Gaetano; Vomero, Salvatore

2013-06-12

61

Reduction of nanofiltration membrane fouling by UV-initiated graft polymerization technique  

Microsoft Academic Search

Nanofiltration polyethersulfone membrane has been modified by means of UV-initiated graft polymerization technique using the weakly acidic monomer acrylic acid and the immersion method. Different UV-irradiation times and acrylic acid concentrations in water were studied. Both the unmodified and the modified polyethersulfone nanofiltration membranes were characterized by attenuated total reflection-Fourier transform infrared spectra (FTIR-ATR) and atomic force microscopy (AFM). Irreversible

M. N. Abu Seman; M. Khayet; Z. I. Bin Ali; N. Hilal

2010-01-01

62

Graft Polymerization of Acrylic Acid on a Polytetrafluoroethylene Panel by an Inductively Coupled Plasma  

NASA Astrophysics Data System (ADS)

Surface modification on a polytetrafluoroethylene (PTFE) panel was performed with sequential nitrogen plasma treatments and surface-initiated polymerization. By introducing COO- groups to the surface of the PTFE panel through grafting polymerization of acrylic acid (AA), a transparent poly (acrylic acid) (PAA) membrane was achieved from acrylic acid solution. Grafting polymerization initiating from the active groups was achieved on the PTFE panel surface after the nitrogen plasma treatment. Utilizing the acrylic acid as monomers, with COO- groups as cross link sites to form reticulation structure, a transparent poly (acrylic acid) membrane with arborescent macromolecular structure was formed on the PTFE panel surface. Analysis methods, such as fourier transform infrared spectroscopy (FTIR), microscopy and X-ray photoelectron spectroscopy (XPS), were utilized to characterize the structures of the macromolecule membrane on the PTFE panel surface. A contact angle measurement was performed to characterize the modified PTFE panels. The surface hydrophilicities of modified PTFE panels were significantly enhanced after the plasma treatment. It was shown that the grafting rate is related to the treating time and the power of plasma.

Lan, Yan; You, Qingliang; Cheng, Cheng; Zhang, Suzhen; Ni, Guohua; Nagatsu, M.; Meng, Yuedong

2011-02-01

63

Preparation of poly(methyl methacrylate) grafted titanate nanotubes by in situ atom transfer radical polymerization  

NASA Astrophysics Data System (ADS)

This paper reports the successful preparation of core-shell hybrid nanocomposites by a 'grafting from' approach based on in situ atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) from titanate nanotubes (TNTs). Transmission electron microscope (TEM) images of the products provide direct evidence for the formation of a core-shell structure, possessing a hard core of TNTs and a soft shell of poly-MMA (PMMA). Fourier-transform infrared spectroscopy (FT-IR), hydrogen nuclear magnetic resonance (1H NMR), scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA) were used to determine the chemical structure, morphology, and the grafted PMMA quantities of the resulting products. The grafted PMMA content was well controlled and increased with increasing monomer/initiator ratio. Further copolymerization of hydroxyethyl methacrylate (HEMA) with PMMA-coated TNTs as initiators was realized, illustrating the 'living' characteristics of the ATRP method used in this paper.

Gao, Yuan; Gao, Xueping; Zhou, Yongfeng; Yan, Deyue

2008-12-01

64

"Grafting-from" Polymerization of PMMA from Stainless Steel Surfaces by a RAFT-Mediated Polymerization Process.  

PubMed

The synthesis of grafted PMMA homopolymer films is reported using a surface-initiated reversible addition-fragmentation chain transfer (SI-RAFT) polymerization from a RAFT-agent immobilized on a silanized stainless steel surface. Therefore, stainless steel surfaces were hydroxylated with piranha solution followed by silanization with 3-aminopropylsilane (APS). The pendant primary amino groups of the cross-linked polysiloxane layer were reacted with 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid N-hydroxysuccinimide ester to produce a surface with covalently immobilized RAFT agents. PMMA homopolymers of different molecular weights between 13?060 and 45?000 g/mol were then prepared by a surface-initiated RAFT polymerization. Molecular weight (MW) and polydispersity index (PDI) were determined from sacrificial polymerization in solution. The different steps of stainless steel surface modification and the ultrathin films were investigated using atomic force microscopy (AFM), static, X-ray photoelectron spectroscopy (XPS), attenuated total reflectance infrared spectroscopy (ATR-IR), and ellipsometry. PMID:24053195

Zammarelli, Nico; Luksin, Michael; Raschke, Hannes; Hergenröder, Roland; Weberskirch, Ralf

2013-10-04

65

Surface modification of poly(styrene-b-(ethylene-co-butylene)-b-styrene) elastomer via photo-initiated graft polymerization of poly(ethylene glycol)  

NASA Astrophysics Data System (ADS)

Poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) copolymer biomedical elastomer was covalently grafted with poly(ethylene glycol) methyl ether methacrylate (PEGMA) via a photo-initiated graft polymerization technique. The surface graft polymerization of SEBS with PEGMA was verified by ATR-FTIR and XPS. Effect of graft polymerization parameters, i.e., monomer concentration, UV irradiation time and initiator concentration on the grafting density was investigated. Comparing with the virgin SEBS film, the PEGMA-modified SEBS film presented an enhanced wettability and a larger surface energy. Besides, the surface grafting of PEGMA imparted excellent anti-platelet adhesion and anti-protein adsorption to the SEBS surface.

Li, Xiaomeng; Luan, Shifang; Yang, Huawei; Shi, Hengchong; Zhao, Jie; Jin, Jing; Yin, Jinghua; Stagnaro, Paola

2012-01-01

66

Entanglements of End Grafted Polymer Brushes in a Polymeric Matrix  

NASA Astrophysics Data System (ADS)

The entanglement of a polymer brush immersed in a melt of mobile polymer chains is studied by molecular dynamics simulations. A primitive path analysis (PPA) is carried out to identify the brush/brush, brush/melt and melt/melt entanglements as a function of distance from the substrate. The PPA characterizes the microscopic state of conformations of the polymer chain and is ideally suited to identify chain/chain entanglements. We use a new thin-chain PPA technique to eliminate spurious non-entangled inter chain contacts arising from excluded volume. As the grafting density of the brush increases we find that the entanglements of the brush with the melt decrease as the system crosses over from the wet to dry brush regime. Results are compared to brush/brush entanglements in an implicit solvent of varying solvent quality. Sandia is a multiprogram laboratory operated by Sandia Corp., a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

Grest, Gary S.; Hoy, Robert S.

2007-03-01

67

[Flocculation of kaolin suspensions by chitosan grafted ternary polymerization flocculant].  

PubMed

Flocculation of kaolin suspensions using ternary polymerization flocculant (CAS) synthesized by chitosan (CTS), acrylamide and ethyl acrylate quaternary ammonium salt was investigated in lab-scale. It was found that CAS had more advantages such as higher flocculation efficiency, lesser dosage and wider pH flocculation range than CTS. CAS was insignificantly exposed to the properties of suspended particles, so preferable flocculation efficiency by it could be obtained both with distilled water and tap water kaolin suspensions. The optimal dosage for CAS was only one-tenth of that of CTS in neutral condition. Good flocculation performance was observed in the pH range of 2.0-11.0 at the dosage of 0.5 mg x L(-1) CAS, and the turbidity removal rates were about 95%. It was also shown that flocculation efficiency was very sensitive to the raw turbidity of kaolin suspensions. At less than 0.5 mg x L(-1) of CAS dose, the higher raw turbidity of the suspension contrarily yielded a lower removing rate. However, when the dosage of CAS was more than 0.5 mg x L(-1), the flocculation efficiency increased with increasing the raw turbidity of kaolin. When the dosage was more than 1.0 mg x L(-1), turbidity removal efficiencies exceeding 85% could be achieved in overall experimental turbidities from 10 to 160 NTU. iPDA-100 device was used to follow the particle aggregation process. And also zeta potential values of particles,floc sizes, shape analyses were presented. It is presumed that the flocculation induced by CAS is dominated by charge patch mechanism and bond bridging. The flocculation reactivity of kaolin suspensions exhibits a dynamic changing, which is simultaneously responsible for several kinds of driving forces. PMID:18637345

Hu, Yong-you; Li, Si-qing; Guo, Yan-ping; Cheng, Jian-hua

2008-04-01

68

Radiation-induced polymerization of 3-octylthiophene  

NASA Astrophysics Data System (ADS)

In order to develop a new synthetic method and to study mechanism of oxidative polymerization of conducting polymers, polymerization of 3-octylthiophene in several organic solvents by ?-irradiation was examined. Polymers bimodal distribution with molecular weights at 500-1000 and 2000-3000 were generated by the irradiation of chloroform solutions. The values of monomer conversion (G(-M)) decreased from 445 to 10 with doses from 0.99 kGy to 594 kGy. The large G(-M) values and dose dependence of G(-M) cannot be explained with widely accepted mechanism for electrochemical polymerization or chemical oxidative polymerization. Another mechanism, which proceeds through chain reactions, is proposed. This mechanism explains the large G(-M) and the dependence on the dose.

Ishigaki, Akihiro; Koizumi, Hitoshi

2012-07-01

69

The use of electron beam lithographic graft-polymerization on thermoresponsive polymers for regulating the directionality of cell attachment and detachment  

Microsoft Academic Search

A simple process for nano-patterned cell culture substrates by direct graft-polymerization has been developed using an electron beam (EB) lithography system requiring no photo-masks or EB-sensitive resists. The compound N-isopropylacrylamide (IPAAm) was locally polymerized and grafted directly by EB lithographic exposure onto hydrophilic polyacrylamide (PAAm)-grafted glass surfaces. The size of the surface grafted polymers was controlled by varying the area

Naokazu Idota; Takahiko Tsukahara; Kae Sato; Teruo Okano; Takehiko Kitamori

2009-01-01

70

Nanocomposites of polystyrene/polystyrene-grafted graphene oxides synthesized by in-situ bulk polymerization.  

PubMed

In this study, polystyrene-grafted graphene oxide (GO-g-PS) nanocomposites with different PS chain lengths were prepared by in-situ polymerization, and their reinforcing effect on the PS matrix was investigated. The glass transition (T(g)) and the thermal degradation (T(d)) temperatures of the PS/GO-g-PS nanocomposites were increased up to 2.8 degrees C and 23.9 degrees C, respectively. The addition of only 0.1 wt% of the GO-g-PS to the PS/GO-g-PS nanocomposites increased the tensile strength and Young's modulus by around 20.5% and 71.4%, respectively. These results showed that the thermal and mechanical properties of the PS/GO-g-PS nanocomposites gradually improved with increasing length of the PS chain grafted onto the GO surface. These differences in reinforcing effects were attributed to differences in interfacial interaction between the graphene and PS matrix. PMID:23755588

Lee, Jaehoon; Yun, Young Soo; Kim, Do Hyeong; Park, Hyun Ho; Jin, Hyoung-Joon

2013-03-01

71

Halloysite nanotubes grafted hyperbranched (co)polymers via surface-initiated self-condensing vinyl (co)polymerization  

Microsoft Academic Search

Halloysite nanotubes (HNTs) grafted hyperbranched polymers were prepared by the self-condensing vinyl polymerization (SCVP)\\u000a of 2-((bromoacetyl)oxy)ethyl acrylate (BAEA) and the self-condensing vinyl copolymerization of n-butyl acrylate (BA) and BAEA with BAEA as inimer (AB*) respectively, from the surfaces of the 2-bromoisobutyric acid modified\\u000a halloysite nanotubes (HNTs-Br) via atom transfer radical polymerization (ATRP) technique. The halloysite nanotubes grafted\\u000a hyperbranched polymer (HNTs-HP)

Bin Mu; Mingfei Zhao; Peng Liu

2008-01-01

72

Graft polymerization of acrylic acid and methacrylic acid onto poly(vinylidene fluoride) powder in presence of metallic salt and sulfuric acid  

Microsoft Academic Search

Poly(vinylidene fluoride) (PVDF) powder was grafted with acrylic acid (AAc) or methacrylic acid (MAA) by the pre-irradiation induced graft polymerization technique. The presence of graft chains was proven by FT-IR spectroscopy. The degree of grafting (DG) was calculated by the acid–base back titration method. The synergistic effect of acid and Mohr's salt on the grafting kinetics was examined. The results

Bo Deng; Yang Yu; Bowu Zhang; Xuanxuan Yang; Linfan Li; Ming Yu; Jingye Li

2011-01-01

73

Artificial cornea: surface modification of silicone rubber membrane by graft polymerization of pHEMA via glow discharge  

Microsoft Academic Search

A method for producing various surfaces of silicone rubber membrane (SR) was developed in this study by grafting various amounts of poly(2-hydroxy ethyl methacrylate) (pHEMA) onto SR by plasma-induced grafted polymerization (PIP) as a homobifunctional membrane. The elemental composition and different carbon bindings on the surface of SR were examined by electron spectroscopy for chemical analysis with the amount of

Shyh-Dar Lee; Ging-Ho Hsiue; Chen-Yu Kao; Patricia Chuen-Tsuei Chang

1996-01-01

74

Immobilization of Yeast Cells with Various Porous Carriers by Radiation-Induced Polymerization.  

National Technical Information Service (NTIS)

Yeast cells were immobilized by radiation-induced polymerization in twice. Various kinds of porous polymer carriers were prepared by radiation-induced polymerization of glass-forming monomers at a low temperature. Precultured yeast cells were incubated ae...

T. Fujimura I. Kaetsu

1982-01-01

75

Solid state polymerization of acrylamide initiated by gamma radiation  

Microsoft Academic Search

The solid-state polymerization of acrylamide, both in a radiation field ; and after removal from the field, is shown to proceed by an unusual kinetic ; mechanism. The usual steady state assumption is found to be inadequate because ; there seems to be no free radical termination (in the normal sense) involved. ; These results are consistent with the view

B. Baysal; G. Adler; D. Ballantine; P. Colombo

1960-01-01

76

Additive effects common to radiation grafting and wood plastic composite formation  

NASA Astrophysics Data System (ADS)

A range of additives has been developed for enhancing grafting yields in a variety of systems initiated by ionizing radiation. Cellulose has been adopted as the predominant naturally occurring model backbone polymer in these studies because of its structural relationship to wood which is the reference substrate for the work reported in the related second part of this paper concerning composites. Some experiments have been performed with the other major naturally occurring polymer, wool. For comparison purposes with synthetic materials, some studies have also been performed with polypropylene as trunk polymer. Styrene has been used as a predominant monomer in grafting with some experiments utilizing the acrylates like methyl methacrylate. The role of solvent in grafting has been evaluated. UV has been used as initiator to replace ionizing radiation for certain experiments. The additives used were mineral acids, lithium salts, multifunctional acrylates and their methacrylate analogues, urea, oligomer acrylates, silane, fluorinated alkyl esters and thermal free radical initiators. A mechanism to explain the additive effect in terms of reagent partitioning has been proposed. The most efficient of the additives in grafting have been applied to the radiation synthesis of wood-polymer composites using two different types of wood, namely simul from Bangladesh and Pinus radiata from Australia with two different monomers with and without solvent, namely butyl methacrylate and methyl methacrylate. The effect of the additives on the physical properties, such as polymer loading and tensile strength, of the wood composites were determined. The partition concept developed for grafting has been used to explain the reactivity of the additives in wood plastic formation. The polymerization of monomers in wood plastic systems is shown to be related to simple homopolymerization of monomers in solution, a reaction which is also shown to be capable of interpretation in terms of partition phenomena.

Garnett, John L.; Loo-Teck, Ng

1996-08-01

77

Dyed acrylic-acid grafted polypropylene films for high-dose radiation dosimetry  

NASA Astrophysics Data System (ADS)

Gamma radiation-induced polymerization of acrylic acid (AAc) onto polypropylene (PP) film has been carried out under nitrogen atmosphere. The grafted film of PP-g-PAAc was allowed to react with solutions of two ionic dyes, namely malachite green (MALG) or methylene green (METG). The investigations show that these new dosimeter films of PPMALG and PPMETG may be useful for high-dose gamma radiation applications. The useful absorbed dose range of the dyed films extends up to about 400 kGy, with a minimum useful dose of about 5 kGy. The radiation-induced colour bleaching has been analyzed with visible spectrophotometry, either at the maximum of the absorption band peaking at 601nm (for PPMETG) or that peaking at 623nm for (PPMALG). The effects of relative humidity during irradiation, shelf-life and post-irradiation storage in dark and indirect daylight conditions on dosimeters performance are discussed.

Abdel-Fattah, A. A.; Said, F. I. A.; Ebraheem, S.; El-Kelany, M.; El Miligy, A. A.

1999-03-01

78

Strategies and techniques to enhance the in situ endothelialization of small-diameter biodegradable polymeric vascular grafts.  

PubMed

Due to the lack of success in small-diameter (<6 mm) prosthetic vascular grafts, a variety of strategies have evolved utilizing a tissue-engineering approach. Much of this work has focused on enhancing the endothelialization of these grafts. A healthy, confluent endothelial layer provides dynamic control over homeo-stasis, influencing and preventing thrombosis and smooth muscle cell proliferation that can lead to intimal hyperplasia. Strategies to improve endothelialization of biodegradable polymeric grafts have encompassed both chemical and physical modifications to graft surfaces, many focusing on the recruitment of endothelial and endothelial progenitor cells. This review aims to provide a compilation of current and developing strategies that utilize in situ endothelialization to improve vascular graft outcomes, providing a context for the future directions of vascular tissue-engineering strategies that do not require preprocedural cell seeding. PMID:23252992

Melchiorri, Anthony J; Hibino, Narutoshi; Fisher, John P

2013-02-13

79

Radiation induced grafting of acrylic acid onto extruded polystyrene surface  

NASA Astrophysics Data System (ADS)

Polystyrene materials with good solubility in liquid scintillation cocktails are used to wipe off different types of surfaces in order to determine the tritium removable contamination with the help of a liquid scintillation counter. This paper analyses hydrophilic surface modifications by radiation induced grafting of acrylic groups onto extruded polystyrene plates. Two grafting methods were used: (a) exposure of extruded polystyrene plates, immersed in aqueous acrylic acid solution, to a gamma radiation of a Co-60 source, and (b) exposure of extruded polystyrene plates to a Co-60 source, followed by the immersion of extruded polystyrene plates in aqueous acrylic acid solution. The grafting of acrylic was proved by IR spectrometry and by radiometric methods using acrylic acid labelled with tritium.

Fugaru, Viorel; Bubueanu, George; Tuta, Catalin

2012-09-01

80

Fragment condensation of peptides on teflon with radiationally grafted polystyrene  

SciTech Connect

In the synthesis of the peptidyl-polymer corresponding to the sequence (57-100) of the ..beta.. chain of human hemoglobin on Teflon with radiationally grafted polystyrene a comparative study was made of different methods of fragment condensation. It was shown that the most effective methods are azide condensation and condensation with the use of complex F.

Sidorova, M.V.; Zheltukhina, G.A.; Filippovich, E.I.; Evstigneeva, R.P.

1986-12-10

81

Radiation chemistry of polymeric components of radioactive waste  

SciTech Connect

The presentation covers fragments of research on the role of radiation chemistry in radioactive waste management. Radioactive waste often contains polymeric materials contaminated with actinides, which exhibit a activity for thousands of years. Rules of safety of transportation and environmental security of permanent storage demand the understanding of radiation chemistry of typical waste matrices. Due to a slow decay and a short range of penetration of a emitters, the experiments with actinides are not easy. 'Therefore, accelerated experiments have been performed using 10 MeV electrons of high intensity. That way chemical effects proceeding over thousands of years could be reduced to minutes in the laboratory. Simulation of the effect of a-radiolysis on polymers by low LET radiation is justified, because low LET radiation produces multi-ionization spurs resulting in the same chemistry as high LET radiation.

Dziewinski, J. J. (Jacek J.); Zagorski, Z. (Zbigniew)

2002-01-01

82

Constructing doxorubicin-loaded polymeric micelles through amphiphilic graft polyphosphazenes containing ethyl tryptophan and PEG segments.  

PubMed

By changing the molar ratio of hydrophilic and hydrophobic segments, a series of novel amphiphilic graft polyphosphazenes (PEG/EtTrp-PPPs) was synthesized via thermal ring-opening polymerization and a subsequent two-step substitution reaction of hydrophilic methoxyl polyethylene glycol (MPEG) and hydrophobic ethyl tryptophan (EtTrp). (1)H-Nuclear magnetic resonance and Fourier transform infrared studies validated the expected synthesis of copolymers. The copolymer composition was also confirmed by UV-visible spectrophotometry. The molar ratio of the segment PEG to group EtTrp was 1.33:0.67, 1.01:0.99 and 0.78:1.22, respectively. Micellization behavior of PEG/EtTrp-PPPs in an aqueous phase was characterized by fluorescence technique, dynamic light scattering and transmission electron microscopy. The critical micelle concentration (CMC) of the graft copolymer in aqueous solution was 0.158, 0.033 and 0.020gl(-1), which decreased as the hydrophobic content in amphiphilic copolymers increased. Doxorubicin (DOX) was physically loaded into micelles prepared by an O/W emulsion method with a drug loading content increasing with DOX feeding. In vitro release of DOX from micelles can be accelerated in weak acidic solution. The results of cytotoxicity study using an MTT assay method with HeLa cell showed that amphiphilic graft polyphosphazenes were biocompatible while DOX-loaded micelles achieved comparable cytotoxicity with that of free DOX. In summary, these novel amphiphilic copolymers exhibited potential to be used as injectable drug carriers for tumor treatment. PMID:19282261

Qiu, Li Yan; Yan, Mei Qiu

2009-02-11

83

Stabilization of alginate beads using radiation polymerized polyacrylamide  

Microsoft Academic Search

A technique has been described for the stabilization of calcium alginate beads using radiation polymerized acrylamide. The technique involved dropping a mixture containing the cells (20%), sodium alginate (2%), acrylamide (2.5%) and N-N?-methylene-bis-acrylamide (0.1%) through a syringe needle into cold (?75°C) toluene. The frozen beads obtained were exposed to 60Co gamma-rays (0.5 KGy) and were then thawed in 0.1 M

Arpita Gupte; Stanislaus F. D’Souza

1999-01-01

84

Surface modification of poly(styrene-b-(ethylene-co-butylene)-b-styrene) elastomer via UV-induced graft polymerization of N-vinyl pyrrolidone.  

PubMed

Poly(N-vinyl pyrrolidone) (PNVP) was covalently grafted onto the surface of biomedical poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) elastomer via a technique of UV-induced graft polymerization combined with plasma pre-treatment. The surface graft polymerization of N-vinyl pyrrolidone (NVP) was confirmed by ATR-FTIR and XPS. Effect of the parameters of graft polymerization, i.e., the initiator concentration, the UV irradiation time and the monomer concentration on the grafting density was investigated. The morphology and the wettability of the PNVP-modified surfaces were characterized by AFM and DSA, respectively. Protein adsorption and platelet adhesion were obviously suppressed after PNVP was grafted onto the SEBS substrates. PMID:22264686

Luan, Shifang; Zhao, Jie; Yang, Huawei; Shi, Hengchong; Jin, Jing; Li, Xiaomeng; Liu, Jingchuan; Wang, Jianwei; Yin, Jinghua; Stagnaro, Paola

2012-01-02

85

Immobilization of Yeast Cells with Hydrophilic Carrier by Radiation-Induced Polymerization.  

National Technical Information Service (NTIS)

Radiation-induced polymerization method was applied to the immobilization of yeast cells. The effects of irradiation, cooling and monomer, which are necessary for polymerization, were recovered completely by subsequent aerobical incubation of yeast cells....

T. Fujimura I. Kaetsu

1981-01-01

86

Enhancement of the grafting performance and of the water absorption of cassava starch graft copolymer by gamma radiation  

Microsoft Academic Search

Enhancement of the gamma radiation grafting of acrylonitrile onto gelatinized cassava starch was investigated. Infrared spectrometry was used to follow the chemical changes in the grafting reaction and from saponification. The saponified starch-g-PAN (HSPAN) was then characterized in terms of grafting parameters to provide a guide for the optimum total dose (kGy) and the appropriate ratio of starch\\/acrylonitrile for a

Suda Kiatkamjornwong; Nispa Meechai

1997-01-01

87

Radiation-induced grafting of acrylamide onto guar gum in aqueous medium: Synthesis and characterization of grafted polymer guar-g-acrylamide  

NASA Astrophysics Data System (ADS)

Mutual radiation grafting technique has been applied to carry out grafting of acrylamide (AAm) onto guar gum (GG) using high-energy Co60? radiation to enhance its flocculating properties for industrial effluents. The grafted product was characterized using analytical probes like elemental analysis, thermal analysis, Fourier transformed infrared (FTIR), X-ray diffraction (XRD) and scanning electron microscope (SEM). The grafting extent was observed to decrease with the dose rate and increase with the concentration of AAm. Thermo gravimetric analysis (TGA) of grafted and ungrafted samples indicated better stability of grafted product. ? and microwave radiation effect on grafted and virgin GG has also been reported.

Biswal, Jayashree; Kumar, Virendra; Bhardwaj, Y. K.; Goel, N. K.; Dubey, K. A.; Chaudhari, C. V.; Sabharwal, S.

2007-10-01

88

Radiation grafting studies of acrylic acid onto cellulose triacetate membranes  

Microsoft Academic Search

Polymer surface modifications were obtained by the application of radiation treatments, etching and grafting of acrylic acid monomers on different membranes of cellulose triacetate materials. Cellulose triacetate foils from pellet dissolution and commercial cellulose triacetate solid state nuclear track detector membranes were assayed. Irradiation with fission fragments from Cf-252 source to obtain a porous structure, 25MeV proton beam and Co-60

R. O Mazzei; E. Smolko; A. Torres; D. Tadey; C. Rocco; L. Gizzi; S. Strangis

2002-01-01

89

Surface treatment of PET fiber by EB-irradiation-induced graft polymerization and its effect on adhesion in natural rubber matrix  

Microsoft Academic Search

Aiming to develop a high performance fiber-reinforced natural rubber (NR) without using resorcinol formaldehyde latex (RFL) adhesives of environmental load substances, a special technique using electron beam (EB) irradiation-induced graft polymerization was applied to high-modulus polyethylene terephthalate (PET) fibers. Although PET is chemically inert, acrylate functional silane could be graft-polymerized onto the PET fiber surface by this special technique. The

Y. Kondo; K. Miyazaki; K. Takayanagi; K. Sakurai

2008-01-01

90

Amphotericin B-incorporated polymeric micelles composed of poly(d,l-lactide-co-glycolide)/dextran graft copolymer.  

PubMed

In this study, we prepared amphotericin B (AmpB)-encapsulated polymeric micelle of poly(d,l-lactide-co-glycolide) (PLGA) grafted-dextran (DexLG) copolymer and characterized its physicochemical properties in vitro. The average particle size of AmpB-encpasulated DexLG polymeric micelles was around 30-150nm while particle size of empty polymeric micelles was below 100nm according to the copolymer composition. The morphology of AmpB-encapsulated polymeric micelle of DexLG copolymer was spherical shapes at transmission electron microscopy (TEM) observation. At 1H NMR study, specific peaks of AmpB and DexLG copolymer was obtained at DMSO but specific peaks characterized to AmpB and PLGA was disappeared at D2O environment. These results indicated that AmpB was encapsulated into the micellar core of polymeric micelle. XRD results also support these results, indicating that specific crystal peaks of AmpB and broad peaks of DexLG copolymer were obtained but specific peaks of AmpB was disappeared at polymeric micelles while physical mixture of AmpB/empty polymeric micelles showed both specific peaks. Drug release rate was decreased according to the increase of drug contents and increase of PLGA component of DexLG copolymer. At the minimal inhibition concentration (MIC) study using Candida albicans, AmpB-encapsulated polymeric micelle showed almost similar effectives on the growth inhibition of microorganisms. These showed that AmpB-encapsulated polymeric micelle of DexLG copolymer can be considered to potential antifungal agent carriers. PMID:18242900

Choi, Ki-Choon; Bang, Je-Yong; Kim, Pyoung-Il; Kim, Chan; Song, Chae-Eun

2007-12-23

91

Radiation-grafted polymers for biomaterial applications. I. 2-hydroxyethyl methacrylate: ethyl methacrylate grafting onto low density polyethylene films  

Microsoft Academic Search

Studies were conducted on the radiation grafting of 2-hydroxyethyl methacrylate (HEMA) and ethyl methacrylate (EMA) by the mutual irradation technique onto low density polyethylene. Four different solution concentrations were used, and radiation doses ranged from 0.03 to 0.50 Mrad. Four copolymer compositions having different HEMA:EMA ratios were also studied using two total monomer concentrations. The kinetics of the grafting process

Daniel Cohn; Allan S. Hoffman; Buddy D. Ratner

1984-01-01

92

Polypropylene membrane surface modification by RAFT grafting polymerization and TiO 2 photocatalysts immobilization for phenol decomposition in a photocatalytic membrane reactor  

Microsoft Academic Search

The main technical barriers that impede photocatalytic membrane reactor (PMR) commercialization remain on the post-recovery of the catalyst particles after water treatment. To overcome this problem, surface modification of polypropylene macroporous membrane was performed with the technique of photoinduced reversible addition-fragmentation chain transfer grafting polymerization of acrylic acid. Titanium oxide photocatalysts were introduced to the acrylic acid grafted membrane surface.

Song Yang; Jia-Shan Gu; Hai-Yin Yu; Jin Zhou; Shi-Feng Li; Xiu-Min Wu; Liang Wang

2011-01-01

93

Radiation-induced grafting of vinylbenzyltrimethylammonium chloride (VBT) onto cotton fabric and study of its anti-bacterial activities  

Microsoft Academic Search

Mutual radiation grafting technique using 60Co gamma radiation has been used to carry out grafting of vinylbenzyltrimethylammonium chloride (VBT) onto cotton cellulose substrate. Grafting yield increased with radiation dose and decreased with dose rate but was adversely affected by the presence of O2 and salts of Fe2+ and Cu2+. However, the presence of an acid did not affect grafting in

Virendra Kumar; Y. K. Bhardwaj; K. P. Rawat; S. Sabharwal

2005-01-01

94

Modification on liquid retention property of cassava starch by radiation grafting with acrylonitrile. I. Effect of ?-irradiation on grafting parameters  

NASA Astrophysics Data System (ADS)

Radiation modification on liquid retention properties of native cassava starch, gelatinized at 85°C, by graft copolymerization with acrylonitrile was carried out by mutual irradiation to gamma-rays. A thin aluminum foil was used to cover the inner wall of the reaction vessel, so that the homopolymer concentration was reduced to be less than 1.0% with a distilled water retention value of 665 g/g of the dry weight of the saponified grafted product. Confirmation of graft copolymerization and saponification reactions was made by the infrared spectrophotometric technique. The combined effect of radiation parameters in terms of an irradiation time and a dose rate to the total dose on the extent of the grafting reaction expressed in terms of grafting parameters which directly influenced liquid retention values was evaluated in conjunction with statistical analysis.

Kiatkamjornwong, S.; Chvajarernpun, J.; Nakason, C.

1993-07-01

95

Macromolecular Nanotechnology Synthesis of polymer grafted carbon nanotubes by nitroxide mediated radical polymerization in the presence of spin-labeled carbon nanotubes  

Microsoft Academic Search

Multiwalled carbon nanotubes (MWCNT) were grafted with polystyrene by in situ nitroxide mediated radical polymer- ization in the presence of TEMPO (2,2,6,6-tetramethylpiperidinyl-1-oxyl) functionalized MWCNT, which was synthesized by the reaction between 4-hydroxyl-TEMPO (HO-TEMPO) and carbonyl chloride groups on the MWCNT. Although the controllability of the polymerization was not high, highly soluble grafted MWCNTs were indeed obtained, indicating that the graft

De-Qin Fan; Jun-Po He; Wei Tang; Jiang-Tao Xu; Yu-Liang Yang

96

Influence of the microenvironment on the activity of enzymes immobilized on Teflon membranes grafted by ?-radiation  

Microsoft Academic Search

The effect of the microenvironment and immobilization method on the activity of immobilized ?-galactosidase was investigated. Immobilization was done on Teflon membranes grafted with different acrylic monomers by ?-radiation and activated by two different coupling agents through the functional groups of the grafted monomers. 2-Hydroxyethyl methacrylate (HEMA) and methacrylic acid (MAA) were grafted on the membrane, and 1,6-hexamethylenediamine (HMDA) was

M. S. Mohy Eldin; M. Portaccio; N. Diano; S. Rossi; U. Bencivenga; A. D'Uva; P. Canciglia; F. S. Gaeta; D. G. Mita

1999-01-01

97

The tolerance of skin grafts to postoperative radiation therapy in patients with soft-tissue sarcoma  

SciTech Connect

During the last ten years at the National Cancer Institute, 11 patients have received 12 courses of postoperative adjuvant radiation therapy to skin grafts used for wound closure after the resection of soft-tissue sarcomas. The intervals between grafting and the initiation of radiation ranged between 3 and 20 weeks, and 4 patients received chemotherapy at the same time as their radiation. Ten of the 12 irradiated grafts remained intact after the completion of therapy. One graft had several small persistently ulcerated areas that required no further surgical treatment, and one graft required a musculocutaneous flap for reconstruction of a persistent large ulcer. Acute radiation effects on the grafted skin sometimes developed at slightly lower doses than usually seen with normal skin, but these acute effects necessitated a break in therapy on only five occasions. Concurrent chemotherapy and a relatively short interval between grafting and the initiation of radiation seemed to contribute to more severe radiation reactions. This experience indicates that postoperative adjuvant radiation therapy can be delivered to skin grafted areas without undue fear of complications, especially if the graft is allowed to heal adequately prior to initiating therapy and if chemotherapy is not given in conjunction with radiation.

Lawrence, W.T.; Zabell, A.; McDonald, H.D. (National Cancer Institute, Bethesda, MD (USA))

1986-03-01

98

A substrate-independent method for surface grafting polymer layers by atom transfer radical polymerization: reduction of protein adsorption.  

PubMed

A general method for producing low-fouling biomaterials on any surface by surface-initiated grafting of polymer brushes is presented. Our procedure uses radiofrequency glow discharge thin film deposition followed by macro-initiator coupling and then surface-initiated atom transfer radical polymerization (SI-ATRP) to prepare neutral polymer brushes on planar substrates. Coatings were produced on substrates with variable interfacial composition and mechanical properties such as hard inorganic/metal substrates (silicon and gold) or flexible (perfluorinated poly(ethylene-co-propylene) film) and rigid (microtitre plates) polymeric materials. First, surfaces were functionalized via deposition of an allylamine plasma polymer thin film followed by covalent coupling of a macro-initiator composed partly of ATRP initiator groups. Successful grafting of a hydrophilic polymer layer was achieved by SI-ATRP of N,N'-dimethylacrylamide in aqueous media at room temperature. We exemplified how this method could be used to create surface coatings with significantly reduced protein adsorption on different material substrates. Protein binding experiments using labelled human serum albumin on grafted materials resulted in quantitative evidence for low-fouling compared to control surfaces. PMID:22023749

Coad, Bryan R; Lu, Yi; Meagher, Laurence

2011-10-11

99

Graft polymerization of acrylic acid and methacrylic acid onto poly(vinylidene fluoride) powder in presence of metallic salt and sulfuric acid  

NASA Astrophysics Data System (ADS)

Poly(vinylidene fluoride) (PVDF) powder was grafted with acrylic acid (AAc) or methacrylic acid (MAA) by the pre-irradiation induced graft polymerization technique. The presence of graft chains was proven by FT-IR spectroscopy. The degree of grafting (DG) was calculated by the acid-base back titration method. The synergistic effect of acid and Mohr's salt on the grafting kinetics was examined. The results indicated that adding sulfuric acid and Mohr's salt simultaneously in AAc or MAA solutions led to a strong enhancement in the degree of grafting. The grafted PVDF powder was cast into microfiltration (MF) membranes using the phase inversion method and some properties of the obtained MF membranes were characterized.

Deng, Bo; Yu, Yang; Zhang, Bowu; Yang, Xuanxuan; Li, Linfan; Yu, Ming; Li, Jingye

2011-02-01

100

Crystal structure and mechanical properties of UHMWPE-g-PMA fiber prepared by radiation grafting  

NASA Astrophysics Data System (ADS)

Methyl acrylate (MA) monomer was grafted onto ultra-high molecular weight polyethylene (UHMWPE) fibers by ?-ray pre-irradiation induced graft polymerization. The grafting of MA on UHMWPE fiber was confirmed by thermogravimetric analysis and Fourier-transform infrared spectroscopy. The degree of grafting (DG) increased with an increase in absorbed dose and reached a significantly high value (approximately 200%) at 100 kGy. Scanning electron microscopy analysis revealed that the surface of the UHMWPE-g-PMA fibers was covered by the MA grafting layer and became rough. The monoclinic crystalline and orientated intermediate phases were disordered by the grafting chains such that degree of orientation declined gradually with increasing DG. The tensile strength of UHMWPE-g-PMA fiber decreased with increasing dose but was independent of DG, whereas the fiber modulus declined with DG. UHMWPE-g-PMA fiber that possesses desirable mechanical properties could be obtained at a dose of less than 10 kGy.

Xing, Zhe; Wang, Mouhua; liu, Weihua; Hu, Jiangtao; Wu, Guozhong

2013-05-01

101

Radiation-induced polymerization for the immobilization of penicillin acylase  

SciTech Connect

The immobilization of Escherichia coli penicillin acylase was investigated by radiation-induced polymerization of 2-hydroxyethyl methacrylate at low temperature. A leak-proof composite that does not swell in water was obtained by adding the cross-linking agent trimethylolpropane trimethacrylate to the monomer-aqueous enzyme mixture. Penicillin acylase, which was immobilized with greater than 70% yield, possessed a higher Km value toward the substrate 6-nitro-3-phenylacetamidobenzoic acid than the free enzyme form (Km = 1.7 X 10(-5) and 1 X 10(-5) M, respectively). The structural stability of immobilized penicillin acylase, as assessed by heat, guanidinium chloride, and pH denaturation profiles, was very similar to that of the free-enzyme form, thus suggesting that penicillin acylase was entrapped in its native state into aqueous free spaces of the polymer matrix.

Boccu, E.; Carenza, M.; Lora, S.; Palma, G.; Veronese, F.M.

1987-06-01

102

Influence of gamma radiation onto polymeric matrix with papain  

NASA Astrophysics Data System (ADS)

Papain is a proteolytic enzyme that has been widely used as debridement agent for scars and wound healing treatment. However, papain presents low stability, which limits its use to extemporaneous or short shelf-life formulations. The purpose of this study was to entrap papain into a polymeric matrix in order to obtain a drug delivery system that could be used as medical device. Since these systems must be sterile, gamma radiation is an interesting option and presents advantages in relation to conventional agents: no radioactive residues are formed; the product can be sterilized inside the final packaging and has an excellent reliability. The normative reference for the establishment of the sterilizing dose determines 25 kGy as the inactivation dose for viable microorganisms. A silicone dispersion was selected to prepare membranes containing 2% (w/w) papain. Irradiated and non-irradiated membranes were simultaneously assessed in order to verify whether gamma radiation interferes with the drug-releasing profile. Results showed that irradiation does not affect significantly papain release and its activity. Therefore papain shows radioresistance in the irradiation conditions applied. In conclusion, gamma radiation can be easily used as sterilizing agent without affecting the papain release profile and its activity onto the biocompatible device is studied.

Zulli, Gislaine; Lopes, Patrícia Santos; Velasco, Maria Valéria Robles; Alcântara, Mara Tânia Silva; Rogero, Sizue Ota; Lugao, Ademar Benévolo; Mathor, Monica Beatriz

2010-03-01

103

Functionalization of cotton fabrics by radiation induced grafting of quaternary salt to impart antibacterial property  

NASA Astrophysics Data System (ADS)

High energy gamma radiation has been used to covalently link polymer chains of a quaternary ammonium salt containing monomer, viz. [2-(Acryloyloxyethyl)]trimethylammonium chloride (AETC) to cotton fabric by mutual radiation grafting using 2-hydroxyethyl methacrylate (2-HEMA) monomer as the grafting facilitator. Grafting yield was found to increase with the radiation dose and monomer concentration. The grafted samples have been characterized for water uptake, surface morphology and thermal stability and for their antibacterial efficacy against various bacteria and were found to possess significant antibacterial activity particularly against gram-positive bacteria.

Goel, N. K.; Kumar, Virendra; Rao, M. S.; Bhardwaj, Y. K.; Sabharwal, S.

2011-11-01

104

Radiation-grafted polymers for biomaterial applications. I. 2-hydroxyethyl methacrylate: ethyl methacrylate grafting onto low density polyethylene films  

SciTech Connect

Studies were conducted on the radiation grafting of 2-hydroxyethyl methacrylate (HEMA) and ethyl methacrylate (EMA) by the mutual irradation technique onto low density polyethylene. Four different solution concentrations were used, and radiation doses ranged from 0.03 to 0.50 Mrad. Four copolymer compositions having different HEMA:EMA ratios were also studied using two total monomer concentrations. The kinetics of the grafting process demonstrated by the two monomers were basically different. While EMA showed a typical diffusion-controlled kinetic pattern, HEMA exhibited a more complex behavior, the main features of which were an induction period, a slight autoacceleration and a significant drop in graft level after a maximum is reached. The difference in behavior was interpreted in terms of partitioning of monomers into the polyethlene substrate. The surface topography of the grafted films was studied by means of scanning electron microscopy. A mechanism based on osmotic cell formation was suggested for the HEMA graft system. The copolymer systems investigated showed that the graft reaction is faster in the initial stages for higher percentages of EMA in the monomer mixtures; as grafting proceeds the trend is reversed. 24 references, 16 figures, 2 tables.

Cohn, D.; Hoffman, A.S.; Ratner, B.D.

1984-08-01

105

Enhancement of the grafting performance and of the water absorption of cassava starch graft copolymer by gamma radiation  

NASA Astrophysics Data System (ADS)

Enhancement of the gamma radiation grafting of acrylonitrile onto gelatinized cassava starch was investigated. Infrared spectrometry was used to follow the chemical changes in the grafting reaction and from saponification. The saponified starch-g-PAN (HSPAN) was then characterized in terms of grafting parameters to provide a guide for the optimum total dose (kGy) and the appropriate ratio of starch/acrylonitrile for a fixed dose rate of 2.5 × 10-1 kGy/min. Other dose rates were also carried out to obtain the appropriate result of grafting copolymerization and of water absorption. A thin aluminium foil, covering the inner wall of the reaction vessel, was found to be far more effective than any other metal films in the enhancement of the grafting reaction and the water absorption as well. Nitric acid in the medium increases the grafting yield and the water absorption. Methyl ether hydroquinone inhibitor was evaluated for its ability to increase homopolymerization and decrease graft reaction. When styrene was used as a comonomer, it hampered the grafting of acrylonitrile onto starch backbone. The water absorption capacity was improved by freeze-drying the HSPAN. The treatment of the HSPAN with aluminium trichloride hexahydrate was found to enhance the degree of wicking, but to decrease the water absorbency.

Kiatkamjornwong, Suda; Meechai, Nispa

1997-06-01

106

Supported neodymium catalysts for isoprene and rac-?-butyrolactone polymerization: modulation of reactivity by controlled grafting.  

PubMed

A series of hybrid materials, bearing neodymium silylamide initiating groups, have been shown to mediate isoprene polymerization when combined with alkyl aluminum activators [methylaluminoxane, AlEt(2)Cl, Al(iBu)(3)]. The surface species nature and relative distribution were correlated with isoprene polymerization activity and selectivity. This approach to stereocontrol modulation has been extended to racemic ?-butyrolactone isoselective ring opening polymerization. PMID:21433143

Terrier, Michael; Brulé, Emilie; Vitorino, Marta J; Ajellal, Noureddine; Robert, Carine; Gauvin, Régis M; Thomas, Christophe M

2010-11-22

107

Effects of triphenylsulfonium hexafluorophosphate in the radiation-induced cationic polymerization of styrene  

SciTech Connect

Radiation-induced cationic polymerization of styrene was studied in methylene chloride in the presence of triphenylsulfonium hexafluorophosphate. Acceleration in polymerization and an increase in molecular weight at a low temperature (- 78/sup 0/C) were observed in the presence of triphenylsulfonium salt. A study of pulse radiolysis revealed that both effects are due mainly to PF/sub 6//sup -/, which forms ion pairs with the cationic species involved in the polymerization.

Mah, S.; Yamamoto, Y.; Hayashi, K.

1982-07-01

108

Synthesis of rapid responsive gels comprising hydrophilic backbone and poly( N-isopropylacrylamide) graft chains by RAFT polymerization and end-linking processes  

Microsoft Academic Search

A thermosensitive poly(N-isopropylacrylamide) (PNIPAM) grafted gel, which comprises hydrophilic backbone and freely mobile PNIPAM graft chains, was synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization and end-linking processes. Functional PNIPAM bearing dithiobenzoate end group (–C(S)S–R) was prepared first, and then it was reacted with divinyl compounds to obtain gel. In order to adjust the composition of the gels, two

Qunfeng Liu; Ping Zhang; Aixiang Qing; Yanxun Lan; Jianbo Shi; Mangeng Lu

2006-01-01

109

Synthesis of polyphenylacetylene by radiation-induced polymerization in deoxycholic acid clathrate  

Microsoft Academic Search

Phenylacetylene was polymerized as inclusion compound (clathrate) inside deoxycholic acid (DOCA) crystals. The polymerization was initiated by ? radiation and a total dose of 320kGy was employed. The resulting polyphenylacetylene (PPA) was isolated by dissolution of deoxycholic acid in boiling ethanol. PPA high polymer was accompanied by a series of phenylacetylene oligomers, which were detected by liquid chromatographic analysis (HPLC).

Franco Cataldo; Giovanni Strazzulla; Susana Iglesias-Groth

2009-01-01

110

Electroless Plating of Copper on Polyimide Film Modified by 50 Hz Plasma Graft Polymerization with 1-Vinylimidazole  

NASA Astrophysics Data System (ADS)

This paper reports on the proof of concept work on the novel process of producing metalized polyimide (PI) film by coating a layer of copper (Cu) thin film on the surface of the PI film without using any adhesive. The method which is employed to produce a metalized PI film used in flexible printed circuit (FPC) is based on plasma graft polymerization of 1-vinlyimidazole (VIDz) on plasma pre-treated PI surface. The plasma grafted PI film (VIDz-g-PI) surfaces are characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and scanning electron microscopy (SEM). AFM results show that the PI film surface has been successfully treated and grafted with VIDz. As post-thermal treatment is known to promote adhesion strength between the metallic film and the PI surface, the effects of post-thermal treatment environment and temperature on the adhesion property of Cu plated VIDz-g-PI (Cu/VIDz-g-PI) are evaluated. Post-thermal treatment in air shows better adhesion strength than in vacuum. The adhesion strength decreases as the post-thermal treatment temperature is increased. In the present development work, the adhesion strength obtained has met the initial market targeted 9-10 N/cm adhesion strength. Samples obtained at a pre-selected plasma power and time window are able to maintain their adhesion strength after being subjected to ageing at 100 °C for 168 h.

Wong, Chiow San; Lem, Hon Pong; Goh, Boon Tong; Wong, Cin Wie

2009-03-01

111

Novel Diblock Copolymer-Grafted Multiwalled Carbon Nanotubes via a combination of Living and Controlled/Living Surface Polymerizations  

SciTech Connect

Diels Alder cycloaddition reactions were used to functionalize multiwalled carbon nanotubes (MWNTs) with 1-benzocylcobutene-10-phenylethylene (BCB-PE) or 4-hydroxyethylbenzocyclobutene (BCB-EO). The covalent functionalization of the nanotubes with these initiator precursors was verified by FTIR and thermogravimetric analysis (TGA). After appropriate transformations/additions, the functionalized MWNTs were used for surface initiated anionic and ring opening polymerizations of ethylene oxide and e-caprolactone (e-CL), respectively. The OH-end groups were transformed to isopropylbromide groups by reaction with 2-bromoisobutyryl bromide, for subsequent atom transfer radical polymerization of styrene or 2-dimethylaminoethyl methacrylate to afford the final diblock copolymers. 1H NMR, differential scanning calorimetry (DSC), TGA, and transmission electron microscopy (TEM) were used for the characterization of the nanocomposite materials. TEM images showed the presence of a polymer layer around the MWNTs as well as the dissociation of MWNT bundles. Consequently, this general methodology, employing combinations of different polymerization techniques, increases the diversity of diblocks that can be grafted from MWNTs.

Priftis, Dimitrios [ORNL; Sakellariou, Georgios [ORNL; Mays, Jimmy [University of Tennessee, Knoxville (UTK); Hadjichristidis, Nikos [University of Athens, Athens, Greece

2010-01-01

112

Generation of functional coatings on hydrophobic surfaces through deposition of denatured proteins followed by grafting from polymerization.  

PubMed

Hydrophilic coatings were produced on flat hydrophobic substrates featuring n-octadecyltrichlorosilane (ODTS) and synthetic polypropylene (PP) nonwoven surfaces through the adsorption of denatured proteins. Specifically, physisorption from aqueous solutions of ?-lactalbumin, lysozyme, fibrinogen, and two soy globulin proteins (glycinin and ?-conglycinin) after chemical (urea) and thermal denaturation endowed the hydrophobic surfaces with amino and hydroxyl functionalities, yielding enhanced wettability. Proteins adsorbed strongly onto ODTS and PP through nonspecific interactions. The thickness of adsorbed heat-denatured proteins was adjusted by varying the pH, protein concentration in solution, and adsorption time. In addition, the stability of the immobilized protein layer was improved significantly after interfacial cross-linking with glutaraldehyde in the presence of sodium borohydride. The amino and hydroxyl groups present on the protein-modified surfaces served as reactive sites for the attachment of polymerization initiators from which polymer brushes were grown by surface-initiated atom-transfer radical polymerization of 2-hydroxyethyl methacrylate. Protein denaturation and adsorption as well as the grafting of polymeric brushes were characterized by circular dichroism, ellipsometry, contact angle, and Fourier transform infrared spectroscopy in the attenuated total reflection mode. PMID:22414148

Goli, Kiran K; Rojas, Orlando J; Ozçam, A Evren; Genzer, Jan

2012-04-04

113

End Grafted Polymer Nanoparticles in a Polymeric Matrix: Effect of Coverage and Curvature  

Microsoft Academic Search

It has recently been proposed that the miscibility of nanoparticles with a polymer matrix can be controlled by grafting polymer chains to the nanoparticle surface. As a first step to study this situation, we have used molecular dynamics simulations on a single nanoparticle of radius R ($4\\\\sigma \\\\le$R$\\\\le 16\\\\sigma$, where $\\\\sigma$ is the diameter of a polymer monomer) grafted with

Joshua Kalb; Douglas Dukes; Sanat K. Kumar; Robert S. Hoy; Gary S. Grest

2010-01-01

114

End Grafted Polymer Nanoparticles in a Polymeric Matrix: Effect of Coverage and Curvature  

Microsoft Academic Search

It has recently been proposed that the miscibility of nanoparticles with a\\u000apolymer matrix can be controlled by grafting polymer chains to the nanoparticle\\u000asurface. As a first step to study this situation, we have used molecular\\u000adynamics simulations on a single nanoparticle of radius R ($4\\\\sigma \\\\le$R$\\\\le\\u000a16\\\\sigma$, where $\\\\sigma$ is the diameter of a polymer monomer) grafted with

Joshua Kalb; Douglas Dukes; Sanat K. Kumar; Robert S. Hoy; Gary S. Grest

2010-01-01

115

Synthesis and Characterization of Block-Graft Copolymers [poly(epichlorohydrin- b -styrene)- g -poly(methyl methacrylate)] by Combination of Activated Monomer Polymerization, NMP and ATRP  

Microsoft Academic Search

Summary  Synthesis of block-graft copolymers, namely poly(epichlorohydrin-b-styrene)-g-poly(methyl methacrylate) (PECH-b-St)-g-PMMA) by combination of Activated Monomer (AM), Nitroxide Mediated Polymerization (NMP) and Atom Transfer Radical Polymerization\\u000a (ATRP) methods was described. For this purpose, first epichlorohydrin (ECH) was polymerized by using BF3THF complex in the presence of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyl-1-oxy (HTEMPO) via AM mechanism. The resulting\\u000a stable radical terminated polymer was subsequently used as a counter

M. Atilla Tasdelen; Yusuf Yagci; A. Levent Demirel; Tadeusz Biedron; Przemyslaw Kubisa

2007-01-01

116

Photochemical modification of poly(ether sulfone) ultrafiltration membranes by UV-assisted graft polymerization for the prevention of biofouling  

NASA Astrophysics Data System (ADS)

Membranes are widely used by the biotechnology industry in the separation and recovery of proteins from biological solutions. Fouling of membrane surfaces by irreversible protein adsorption during ultrafiltration causes loss of membrane permeability and can reduce membrane selectivity and lead to significant product loss through denaturation. In this work, low fouling poly(ether sulfone) (PES) ultrafiltration membranes were produced by ultraviolet (UV) assisted graft polymerization of hydrophilic vinyl monomers using a newly developed photochemical dip modification technique. This technique was developed to make the UV modification process more easily adaptable to continuous membrane manufacturing processes. A method was also developed to measure and track the degree of polymer grafting on the membrane surface using attenuated total reflection Fourier transform infrared spectroscopy (FTIR/ATR). Grafting the hydrophilic monomer N-vinyl-2-pyrrolidinone (NVP) onto the membrane surface increased surface wettability and produced membranes with the high wettability of regenerated cellulose membranes. The enhanced surface wettability significantly decreased irreversible adsorptive fouling during the filtration of the protein bovine serum albumin (BSA). In order to maintain the rejection of BSA after modification, PES chain scission was tightly controlled by regulating the UV wavelength range and the light intensity used. The UV reactor system was operated with 300 nm UV lamps and a benzene filter used to remove high energy wavelengths below 275 nm that were determined to cause severe loss of BSA rejection due to pore enlargement from extensive chain scission. Dip modification caused membrane permeability to decrease due to the grafted chains blocking the membrane pores. The use of a chain transfer agent during modification followed by ethanol cleaning increased modified membrane permeability, but BSA rejection was severely decreased. The resultant membranes produced by dip modification using this new UV reactor configuration exhibited higher rejection, similar permeability, and similar irreversible fouling as regenerated cellulose membranes, the lowest fouling commercial ultrafiltration membranes currently available. Therefore, these modified membranes can be used as an alternative to regenerated cellulose membranes in the ultrafiltration of protein solutions.

Pieracci, John Paul

117

In vitro release studies of vitamin B12 from poly N-vinyl pyrrolidone/starch hydrogels grafted with acrylic acid synthesized by gamma radiation  

NASA Astrophysics Data System (ADS)

Co-polymeric hydrogels containing N-vinyl pyrrolidone and starch grafted with acrylic acid were synthesized by gamma radiation to be used as drug delivery system. Their gel contents, grafting swelling and thermal gravimetric analysis were evaluated. The gel content increases by increasing the irradiation dose up to 50 kGy, then decreases. The grafting percent increases by the increasing of acrylic acid. The thermal stability and the rate of the thermal decomposition changed according to the different compositions. The maximum rate of the thermal decomposition decreases by increasing the irradiation dose from 20 to 30 kGy and increases by increasing the irradiation dose from 30 to 70 kGy. The hydrogels loaded with vitamin B12 demonstrated a decrease release in acidic medium than the neutral one.

Eid, M.

2008-12-01

118

Radiation Grafting of Acrylonitrile onto Polyester Fiber as the Reinforcing Filler for Poly (Vinyl Chloride).  

National Technical Information Service (NTIS)

Studies have been carried out on radiation-induced grafting of acrylonitrile onto polyester fiber and on the properties of the grafted fiber in an attempt to increase the strength of polyester fiber reinforced soft poly (vinyl chloride) (PVC) sheet by imp...

K. Kaji I. Ando

1985-01-01

119

Usefulness of microporous hydrophobic polypropylene membranes after plasma-induced graft polymerization of acrylic acid for high-power nickel–cadmium batteries  

Microsoft Academic Search

Commercial microporous polypropylene (PP) membranes were modified by plasma-induced graft polymerization of acrylic acid (AAc) under UV irradiation. Under optimized conditions obtained membranes are hydrophilic and may be serviceable as separator in nickel–cadmium cell. Electrolytic resistance of modified membranes is evaluated and compared with that of commercial separators: conventional cellophane separation and hydrophilic polypropylene separation (Celgard 3501). This paper reports

Aleksander Ciszewski; Jerzy Kunicki; Irena Gancarz

2007-01-01

120

Analysis of a Styrene-Butadiene Graft Copolymer by Size Exclusion Chromatography II. Determination of the Branching Exponent with the Help of a Polymerization Model  

Microsoft Academic Search

A styrene — butadiene graft copolymer is analyzed by size exclusion chromatography (SEC) with on-line viscometry with the aim of estimating the ? exponent that relates the two branching parameters through g = g?. Three copolymer samples synthesized in a solution polymerization of styrene in the presence of polybutadiene were analyzed. Theoretical predictions on the branching characteristics were obtained with

J. R. Vega; D. A. Estenoz; H. M. Oliva; G. R. Meirra

2001-01-01

121

Radiation initiated graft copolymerization of N-vinylpyrrolidone and acrylamide onto low density polyethylene films by individual and binary system  

Microsoft Academic Search

A study has been made for the preparation of membranes by the direct radiation grafting of N-vinyl pyrrolidone (NVP), acrylamide (AAm) and its comonomer onto low density polyethylene (LDPE) films. The factors affecting the grafting process such as solvent, inhibitor, radiation dose, dose rate, monomer and comonomer concentrations on the grafting yield were studied. Dioxane was chosen as a diluent

N. H. Taher; A. M. Dessuoki; M. B. El-Arnaouty

1998-01-01

122

Chemical Properties and Film Casting of Radiation Grafted Ion-Containing Polymers.  

National Technical Information Service (NTIS)

A series of radiation grafted cation and anion exchange polymers have been studied with the intent of developing procedures for dissolving and film casting these polymers. Solvent swelling studies have shown that these polymers display two maxima in plots...

M. N. Szentirmay C. R. Martin

1984-01-01

123

Fabrication of conducting poly(3-thiophene boronic acid)-grafted multi-walled carbon nanotubes by oxidative polymerization.  

PubMed

Composite materials of multi-walled carbon nanotubes (MWNTs) and a conducting polymer, poly(3-thiophene boronic acid) (PTBA) were prepared by in-situ oxidative polymerization of TBA in the presence of MWNTs and potassium dichromate. The MWNTs which were previously surface functionalized with acid chloride groups were reacted with TBA using a simple "chemical grafting" technique. It was observed that the nanotubes were dispersed uniformly in the pi-conjugated polymer matrix and entrapped by the polymer. The conductivity of the composites was higher than that of the pure polymer from a conventional four-probe technique, which indicates that the fabrication of MWNTs into the polymer matrix significantly improves the conductivity of the polymer due to the intrinsic properties of MWNTs. PMID:22524052

Niranjanmurthi, Lingappan; Choi, Byung Chun; Park, Jong Myung; Lim, Kwon Taek

2012-01-01

124

Radical graft polymerization of an Allyl Monomer onto Hydrophilic Polymers and their antibacterial nanofibrous membranes  

Technology Transfer Automated Retrieval System (TEKTRAN)

Hydrophilic poly (vinyl alcohol-co-ethylene) (PVA-co-PE) copolymers with 27 mol %, 32 mol % and 44 mol % ethylene were functionalized by melt radical graft copolymerization with 2,4-diamino-6-diallylamino-1,3,5-triazine (NDAM) using reactive extrusion. This functionalization imparts antibacterial pr...

125

Functionalization of Graphene Sheets via Chemically Grafting of PMMA Chains Through in-situ Polymerization  

Microsoft Academic Search

In this work, we report the preparation of graphene nanoplatelet which covalently functionalized with PMMA chains by introduction of vinyl groups onto graphene surface through simple esterification reaction between hydroxyl groups of graphite oxide and methacrylic anhydride. The synthesis is followed by in-situ polymerization with MMA monomers. The structural properties were characterized with X-ray diffraction spectroscopy (XRD) and scanning electronic

S. Mohamadi; N. Sharifi-Sanjani; H. Mahdavi

2011-01-01

126

Effect of solvents on the radiation-induced polymerization of ethyl and isopropyl vinyl ethers  

SciTech Connect

The effect of solvents on the radiation-induced cationic polymerization of ethyl and isopropyl vinyl ethers (EVE and IPVE, respectively) was investigated. EVE and IPVE polymerizations were carried out in bulk and in solution under superdry conditions in which polar impurities, especially water, have been reduced to negligible levels. This was accomplished by means of a sodium mirror technique using joint free baked out glass equipment and high vacuum. Plots of the monomer conversions and irradiation times were obtained for EVE and IPVE polymerizations in bulk and in benzene solution at constant monomer concentrations. The monomer concentration dependence of the polymerization rate was studied for EVE polymerization in bulk and in benzene, diethlyl ether, diglyme and methylene chloride, and for IPVE polymerization in bulk and in benzene. Solvent effect on the estimated propagating rate constants was examined for EVE and IPVE polymerization in bulk and in solution. The effect of temperature on the polymerization rate was also investigated for EVE polymerization in bulk ad in benzene, diethyl and diisopropyl ethers, methylene chloride and nitromethane, and for IPVE ploymerization in bulk and in benzene.

Hsieh, W.C.

1981-01-01

127

Zwitterionic sulfobetaine-grafted poly(vinylidene fluoride) membrane surface with stably anti-protein-fouling performance via a two-step surface polymerization  

NASA Astrophysics Data System (ADS)

A zwitterionic polymer, poly(3-(methacryloylamino) propyl-dimethyl-(3-sulfopropyl) ammonium hydroxide) (poly(MPDSAH)) was successfully grafted in high density from the surface of poly(vinylidene fluoride) (PVDF) hollow fiber membrane via a two-step polymerization. Poly(2-hydroxyethyl methacrylate) (poly(HEMA)) chains were firstly grafted from outside surface of PVDF membrane through atom transfer radical polymerization (ATRP) to provide the initiation sites for subsequent cerium (Ce (IV))-induced graft copolymerization of polyMPDSAH in the presence of N,N?-ethylene bisacrylamide (EBAA) as a cross-linking agent. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) confirmed that the EBAA could stimulate zwitterionic polymers grafting onto the membrane surface. The dense poly(MPDSAH) layers on the PVDF membrane surface were revealed by the scanning electron microscope (SEM). The mechanical property of PVDF membrane was improved by the zwitterionic surface layers. The gravimetry results indicated the grafting amount increased to 520 ?g/cm2 for a copolymerization time of more than 3 h. Static and dynamic water contact angle measurements showed that the surface hydrophilicity of the PVDF membranes was significantly enhanced. As the grafting amount reached 513 ?g cm-2, the value of contact angle dropped to 22.1° and the amount of protein adsorption decreased to zero. The cyclic experiments for BSA solution filtration demonstrated that the extent of protein fouling was significantly reduced and most of the fouling was reversible. The grafted polymer layer on the PVDF membrane showed a good stability during the membrane cleaning process. The experimental results concluded a good prospect in obtaining the sulfobetaine-modified PVDF membranes with high mechanical strength, good anti-protein-fouling performance, and long-term stability via the two-step polymerization.

Li, Qian; Bi, Qiu-Yan; Zhou, Bo; Wang, Xiao-Lin

2012-03-01

128

Cell engineering: nanometric grafting of poly-N-isopropylacrylamide onto polystyrene film by different doses of gamma radiation.  

PubMed

Poly-N-isopropylacrylamide was successfully grafted onto a polystyrene cell culture dish and ?-preirradiated in air. In this study, the effect of a ?-pre-irradiation dose of radiation (radiation absorbed dosages of 10, 20, 30, 40 KGy) under appropriate temperature and grafting conditions was investigated. The Fourier transform infrared spectroscopy analysis showed the existence of the graft poly-N-isopropylacrylamide (PNIPAAm) on the substrate. The optimal value of the dose for grafting was 40 KGy at 50°C. The scanning electron microscopy and atomic force microscopy (AFM) images clearly showed that increasing the absorbed dose of radiation would increase the amount of grafting. Surface topography and graft thickness in AFM images of the radiated samples showed that the PNIPAAm at the absorbed dose of radiation was properly grafted. The thickness of these grafts was about 50-100 nm. The drop water contact angles of the best grafted sample at 37°C and 10°C were 55.3 ± 1.2° and 61.2 ± 0.9° respectively, which showed the hydrophilicity and hydrophobicity of the grafted surfaces. Differential scanning calorimetry analysis also revealed the low critical solution temperature of the grafted sample to be 32°C. Thermoresponsive polymers were grafted to dishes covalently which allowed fibroblast cells to attach and proliferate at 37°C; the cells also detached spontaneously without using enzymes when the temperature dropped below 32°C. This characteristic proves that this type of grafted material has potential as a biomaterial for cell sheet engineering. PMID:20957116

Biazar, Esmaeil; Zeinali, Reza; Montazeri, Naser; Pourshamsian, Khalil; Behrouz, Mahmoud Jabarvand; Asefnejad, Azadeh; Khoshzaban, Ahad; Shahhosseini, Gholamreza; Najafabadi, Mostafa Soleimannejad; Abyani, Reza; Jamalzadeh, Hamidreza; Fouladi, Mahdi; Hagh, Sasan Rahbar F; Khamaneh, Aylar Shams; Kabiri, Soudabeh; Keshel, Saeed Heidari; Mansourkiaei, Ana

2010-08-09

129

Grafted Polymeric Microspheres: A Synthetic Approach to Structurally Well-Defined Brush Polymers  

Microsoft Academic Search

A simple method for the surface grafting of crosslinked polystyrene latex particles of narrow size distribution as core is described. Amino groups were generated on the surface of these microspheres by a two-step process of nitration and subsequent reduction. Polyethylene glycol chain of desired molecular weight was covalently linked to the surface amino group using diiso-cyanate-coupling reaction. The method is

K. N. Jayachandran; P. R. Chatterji

1998-01-01

130

Enhancing antifouling property of polysulfone ultrafiltration membrane by grafting zwitterionic copolymer via UV-initiated polymerization  

Microsoft Academic Search

A new kind of zwitterionic molecule, [3-(methacryloylamino)propyl]-dimethyl (3-sulfopropyl) ammonium hydroxide inner salt (MPDSAH) was grafted onto polysulfone (PSF) ultrafiltration membrane surface using benzophenone (BP) as the initiator to improve the antifouling property. Polymer chain scission was suppressed by H-abstraction from methyl groups under long-wavelength UV irradiation (?>300nm), which avoided the photodegradation of PSF ultrafiltration membrane. The effects of MPDSAH concentration,

Haijun Yu; Yiming Cao; Guodong Kang; Jianhui Liu; Meng Li; Quan Yuan

2009-01-01

131

Biobased grafted polyesters prepared by in situ ring-opening polymerization  

Microsoft Academic Search

EVA-g-PLA and EVA-g-PCL copolymers were synthesized by in situ polymerization of ?-caprolactone and lactide, in the presence of molten ethylene vinyl acetate (EVA) copolymer, using titanium phenoxide (Ti(OPh)4) as initiator. The materials prepared in a internal batch mixer were characterized by 1H NMR, SEM, FTIR, rheology, DSC, TGA and SEC and the synthesized copolymers identified through selective extraction. The mechanical

I. Moura; R. Nogueira; V. Bounor-Legare; A. V. Machado

2011-01-01

132

TEMPO addition into pre-irradiated fluoropolymers and living-radical graft polymerization of styrene for preparation of polymer electrolyte membranes  

NASA Astrophysics Data System (ADS)

We prepared proton exchange membranes (PEMs) by 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO)-mediated living-radical graft polymerization (LRGP) of styrene into fluoropolymer films and subsequent sulfonation. Poly(vinylidene fluoride) (PVDF) and poly(ethylene-co-tetrafluoroethylene) (ETFE) films were first irradiated and then treated with TEMPO solutions in various solvents. TEMPO addition was confirmed by the test of styrene grafting into TEMPO-treated films at 60 °C, at which the LRGP never proceeds. This test enabled us to differentiate the LRGP from the conventional graft polymerization. In order to gain a deep insight about TEMPO-addition reaction, the TEMPO-penetration behavior into the base polymer films was examined by a permeation experiment and computer simulation. Xylene and dioxane were appropriate solvents for the complete introduction of TEMPO into PVDF and ETFE films, respectively. Then, the LRGP of styrene was performed based on the fully TEMPO-capped films at 125 °C with various solvents. By using an alcoholic solvent, the degree of grafting was enhanced and it reached a maximum of 38%. This grafted film was sulfonated to prepare a PEM showing an ion exchange capacity of 2.2 meq/g and proton conductivity of 1.6×10-1 S/cm.

Sawada, Shin-Ichi; Suzuki, Akihiro; Terai, Takayuki; Maekawa, Yasunari

2010-04-01

133

Thermal free radical initiators as accelerators in radiation grafting reactions: Relevance in analogous curing processes  

NASA Astrophysics Data System (ADS)

Two thermal free radical initiators, namely ammonium persulphate (APS) and 2,21-azobisisobutyronitrile (AIBN) are shown to represent a new class of additives capable of enhancing radiation grafting yields. Their reactivities are compared with those of previously reported additives. The data are of interest to analogous radiation curing processes.

Chaplin, R. P.; Gamage, N. J. W.; Garnett, J. L.

1995-09-01

134

Polymer-grafted silica: A screening system for polymeric adsorption resin development  

SciTech Connect

A screening-level methodology was developed for the evaluation of solute affinity for polymers that are candidate sorption resins. In this approach novel grafted polymer-silica resins were synthesized to produce poly(vinylpyrrolidone)-silica (PVP-Si) and poly(vinyl acetate)-silica (PVAc-Si) resins. The polymer-silica resins along with a number of commercially available polymer resins were used to evaluate the aqueous-phase adsorption of phenol, tetrachloroethene (PCE), trichloroethene (TCE), and chloroform. The polymer-grafted silicas were able to selectively remove pollutants from water with a covalently bonded polymer layer that has a high affinity for the target pollutant. The PVAc-silica resin had a sorption capacity for TCE and CHCl[sub 3] as high as commercial poly(styrene) resin XAD-4; the PVP-Si resin had a sorption capacity for phenol higher than a commercial poly-(vinylpyridine) resin (Reillex 425). PCE adsorption onto the PVAc-silica was comparable to the commercial poly(methacrylate) and poly(vinylpyridine) resins but less than the poly(styrene) resin. The results show that the Hildebrand solubility parameter along with the dipole moment of the polymer functional groups can be used for an initial screening-level assessment of polymer-solute affinity.

Browne, T.E.; Cohen, Y. (Univ. of California, Los Angeles (United States))

1993-04-01

135

Preparation and characterization of supported hydrogels obtained by radiation grafting of binary monomers  

Microsoft Academic Search

The preparation and characterization of supported hydrogels obtained by radiation-induced graft copolymerization of styrene\\/maleic anhydride (Sty\\/MAn) binary monomers system onto low density polyethylene films were investigated. Attention was focused on the selection of the reaction parameters suitable for the commercial production of such hydrogels. The factors which affect the preparation process and grafting yield are type of solvent, dose rate,

El-Sayed A Hegazy; H. A Abd El-Rehim; N. A Khalifa; A El-Hag Ali

1999-01-01

136

Removal of hazardous metal ions from wastewater by radiation synthesized silica-graft-dimethylaminoethyl methacrylate adsorbent  

Microsoft Academic Search

Silica-based adsorbent was prepared by radiation-induced grafting of dimethylaminoethyl methacrylate (DMAEMA) onto silanized silica (SS). The SS was pre-irradiated by electron beam (EB) and then reacted with DMAEMA solution at various conditions. The FTIR and TG-DTA spectra manifested that DMAEMA was successfully grafted onto the SS surface. Three kinds of typical hazardous metal ions (Cr (VI), As (V) and Hg

Long Zhao; Jian Sun; Yinghui Zhao; Ling Xu; Maolin Zhai

2011-01-01

137

CT complexes in radiation polymerisation processes including grafting, curing and hydrogel formation  

NASA Astrophysics Data System (ADS)

Parameters influencing the grafting of a typical charge transfer (CT) complex, maleic anhydride /triethylene glycol divinyl ether, to representative substrates, cellulose and polypropylene, initiated by UV and ionising radiation have been investigated. The variables studied include effect of solvent, role of donor involving the type of ether and the nature of the acceptor including the use of common monomers like methyl methacrylate. A novel application of this CT grafting work is reported involving hydrogel formation with subsequent controlled release of incorporated reagent.

Garnett, John L.; Ng, Loo-Teck; Nguyen, Duc; Swami, Salesh; Zilic, Elvis F.

2002-03-01

138

Immobilization of enzymes to porous-bead polymers and silica gels activated by graft polymerization of 2,3-epoxypropyl methacrylate.  

PubMed

Three types of organic polymers and bead-shape silica gels were activated by graft polymerization of 2,3-epoxypropyl methacrylate; in some cases, epoxide groups on the support surface were modified to NH2 groups. Eight active matrices so obtained were assessed as supports for immobilized enzymes using peroxidase, glucoamylase and urease. The immobilization yield of protein and specific activities of enzymes were better with supports containing NH2 groups than with those containing epoxide spacer arms. Maximum enzyme immobilization and storage stabilities were obtained with silica-gel beads activated by graft polymerization of 2,3-epoxypropyl methacrylate. With all eight matrices tested, the immobilized enzymes showed good stability with not less than 82% of the original activity persisting after 28 days. The developed matrices have potential for use in process-scale biotechnological operations. PMID:1369257

Wójcik, A; Lobarzewski, J; B?aszczy?ska, T

1990-01-01

139

Bioresponse to polymeric substrates: Effect of surface energy, modulus, topography, and surface graft copolymers  

NASA Astrophysics Data System (ADS)

Biofouling is the accumulation of biological matter on a substrate. It is essential to elucidate and model the major factors that affect both biological settlement and adhesion to substrates in order to develop coatings that minimize initial fouling or ease the removal of this fouling. To date, models that have estimated adhesion strength to coatings primarily included bulk elastic modulus and surface energy. Topography, however, has been found to dominate both these terms in the reduction of settlement and has been found to affect the adhesion strength as well. Silicone foul release coatings have demonstrated moderate success in the prevention of marine biofouling because of their low modulus and low surface energy. Problems exist with durability and eventual fouling of the coating due to the overgrowth of foulants that prefer hydrophobic substrates. This research details the characterization and the surface and bulk modification of a commercially available silicone elastomer. The modifications include bulk additives, surface topography, and surface graft copolymers. The effect of these modifications on biological response was then assayed using the alga Ulva as a model for marine biofouling. The unmodified silicone elastomer has a bulk modulus of approximately 1 MPa. The addition of vinyl functional polydimethylsiloxane oils allowed for a greater than 200% increase or a 90% decrease in the bulk modulus of the material. The addition of non-reactive polydimethylsiloxane oils allowed for a change in the surface lubricity of the elastomer without a significant change in the mechanical properties. Topographical modifications of the surface show a profound effect on the bioresponse. Appropriately scaled engineered microtopographies replicated in the silicone elastomer can produce a 250% increase in algal zoospore fouling or an 85% reduction in settlement relative to a smooth silicone elastomer. Finally, the modification of the surface energy of this material was achieved by acid catalyzed surface hydrolysis and subsequent grafting of poly(ethylene glycol), polysulfone, or perfluoropolyether. The water contact angle could be increased by 16% or decreased by 60% relative to the silicone elastomer control. These surfaces were characterized by various contact angle techniques, ATR-FTIR, and XPS. These surface grafts were also combined with the topographical modifications to evaluate the relative significance of these two factors on bioresponse.

Wilson, Leslie Hoipkemeier

140

UV radiation induced surface modulation time evolution in polymeric materials  

NASA Astrophysics Data System (ADS)

The reorganization processes at submicron level of the polymeric materials have been investigated because of their applications in optoelectronics and bio-science. We have obtained surface relief modulation in single step processing on the photo resist and polysiloxane films. But for technical applications the time evolution and stability of the induced surface structure is an important parameter and is a problem to be discussed. In case of single step surface relief formation on polymeric materials the process is connected with the photochromic behavior of the materials. As it is known the UV light induced effects on the material structure are reversible under the action of visible light, but with different speeds. In this report is analyzed the time evolution of the surface modulation obtained under the action of the UV light for azopolymers with different structures.

Apostol, I.; Apostol, D.; Damian, V.; Iordache, I.; Hurduc, N.; Sava, I.; Sacarescu, L.; Stoica, I.

2010-11-01

141

New Applications of Ring-Opening Metathesis Polymerization for Grafting Alkylene Oxide-Based Copolymers  

NASA Astrophysics Data System (ADS)

This research tackles the challenges of innovative modification of poly(allyl alkylene oxides) by ROMP to produce new materials. Firstly, binary and ternary copolymers, poly(epichlorohydrin-allyl glycidyl ether) (ECH-AGE) and poly (epichlorohydrin-propylene oxide-allyl glycidyl ether) (ECH-PO-AGE), have been prepared using as initiator a catalytic system consisting of an alkyl aluminium, controlled amounts of water and different compounds (ethers, diols, phosphines, salicylic acid derivatives, organozincs) acting as cocatalysts. Among catalysts explored in these copolymerizations most productive showed to be the systems triisobutylaluminium (TIBA), water and Zn(DIPS)2 or Zn(acac)2. Copolymers which have become thus available were subsequently grafted onto the pendent allylic groups by ROMP with cycloolefins (cyclooctene, norbornene, cyclododecene) involving ruthenium based catalysts.

Spurcaciu, Bogdan; Buzdugan, Emil; Nicolae, Cristian; Ghioca, Paul; Iancu, Lorena; Dragutan, Valerian; Dragutan, Ileana

142

Hyper-branched poly(poly(ethylene glycol)methacrylate)-grafted surfaces by photo-polymerization with iniferter for bioactive interfaces  

Microsoft Academic Search

A new hyper-branched surface in which three species of architectures were constructed as stem chain, branched stem and twig chain-grafted branched chain of poly(poly(ethylene glycol)methacrylate) (poly(PEGMA)) by photo-polymerization using dithiocarbamyl group (DC) as iniferter was prepared and characterized. For these surfaces, radical copolymerization of styrene and an iniferter-activated chain that was previously synthesized was performed for using as base materials

Yoon Ki Joung; Jong Hoon Choi; Jin Woo Bae; Ki Dong Park

2008-01-01

143

Precise synthesis of polymers containing functional end groups by living ring-opening metathesis polymerization (ROMP): Efficient tools for synthesis of block\\/graft copolymers  

Microsoft Academic Search

This article summarizes recent examples for precise synthesis of (co)polymers containing functional end groups prepared by living ring-opening metathesis polymerization (ROMP) using molybdenum, ruthenium complex catalysts. In particular, this article reviews recent examples for synthesis of amphiphilic block\\/graft copolymers by adopting transition metal-catalyzed living ROMP technique. Unique characteristics of the living ROMP initiated by the molybdenum alkylidene complexes (so-called Schrock

Kotohiro Nomura; Mohamed Mehawed Abdellatif

2010-01-01

144

MODIFICATION OF COTTON WITH ACRYLONITRILE BY RADIATION POLYMERIZATION  

Microsoft Academic Search

The modification of cellulose (cotton fabric or yarn) was carried out ; with acrylonitrile under ionizing radiation. Irradiation of the cotton in ; aqueous acrylonitrile solutions with gamma or electron radiation produces a ; modified cotton with improved rot and mildew resistance similar to that of ; cyanoethylated cotton. Strength properties are not significantly affected, ; provided the radiation dose

F. L. Saunders; R. C. Sovish

1963-01-01

145

Hyper-branched poly(poly(ethylene glycol)methacrylate)-grafted surfaces by photo-polymerization with iniferter for bioactive interfaces.  

PubMed

A new hyper-branched surface in which three species of architectures were constructed as stem chain, branched stem and twig chain-grafted branched chain of poly(poly(ethylene glycol)methacrylate) (poly(PEGMA)) by photo-polymerization using dithiocarbamyl group (DC) as iniferter was prepared and characterized. For these surfaces, radical copolymerization of styrene and an iniferter-activated chain that was previously synthesized was performed for using as base materials for surface coating. On a DC-activated surface, hyper-branched poly(PEGMA) was introduced by photo-polymerization and dithiocarbamylation. All modified surfaces were analyzed by X-ray photoelectron spectroscopy (XPS) and water contact angle measurements. Our results demonstrated that a highly hyper-branched graft architecture of poly(PEGMA) can be constructed on PU surface by photo-polymerization using dithiocarbamyl group as iniferter, in which first, second and third generation gave stem chain, branched chain and twig chain of poly(PEGMA), respectively. Our hyper-branched surfaces could be regulated by photo-irradiation time and might be controlled by feed amounts or other reaction conditions. This highly dense architecture of PEG chain with hydrophilicity and chain mobility, grafted on surface, is expected to be effectively utilized in bio-implantable substrates or micro- or nano-patterned surfaces for immobilization of bioactive molecules in biomedical fields. PMID:18337197

Joung, Yoon Ki; Choi, Jong Hoon; Bae, Jin Woo; Park, Ki Dong

2008-03-03

146

Benzophenone absorption and diffusion in poly(dimethylsiloxane) and its role in graft photo-polymerization for surface modification.  

PubMed

Following the great success of traditional microfluidic devices across many disciplines, a new class of microfluidic systems emerged in recent years, which features finely tuned, localized surface modifications within the microstructures in order to keep up with the demand for devices of ever increasing complexity (lab on chip, assay on chip, etc.). Graft photopolymerization has become a powerful tool for such localized surface modifications particularly in combination with poly(dimethylsiloxane) (PDMS) devices, as it is compatible with many functional monomers and allows for high spatial resolution. However, application within enclosed PDMS microstructures and in particular well-controlled surface-directed polymerization remains challenging. Detailed understanding of the interaction between photoinitiator, benzophenone (BP), and polymer matrix is needed. We have developed a visualization technique, which allows for observation of reacted BP in situ within the PDMS matrix. We present a detailed study on solvent-driven BP diffusion providing results essential to successful surface treatment. We also identified and investigated photoinitiator inhibition by oxygen and provide appropriate mitigation strategies. PMID:21207954

Schneider, Marc H; Tran, Yvette; Tabeling, Patrick

2011-01-05

147

Influence of Space Radiation on the Outgassing Rate of a Patterned Polymeric Composite in Vacuum  

SciTech Connect

Experimental results on outgassing rates of patterned polymeric composites preliminary subjected to separate and combined radiation have been analyzed and presented. Mathematical models describing the outgassing processes in these materials were used for interpretation of the experimental data. Numerical results found using the models are presented.

Khasanshin, R. H.; Timofeev, A. N. [Joint-stock company 'Kompozit' 4, Pionerskay str., 141070 Korolev, Moscow region, Russia, tel. 513-20-20 (Russian Federation); Ivanov, M. F. [Joint Institute for High Temperatures of Russian Academy of Sciences Moscow (Russian Federation)

2009-01-05

148

Functional polymer brushes via surface-initiated atom transfer radical graft polymerization for combating marine biofouling.  

PubMed

Dense and uniform polymer brush coatings were developed to combat marine biofouling. Nonionic hydrophilic, nonionic hydrophobic, cationic, anionic and zwitterionic polymer brush coatings were synthesized via surface-initiated atom transfer radical polymerization (SI-ATRP) of 2-hydroxyethyl methacrylate, 2,3,4,5,6-pentafluorostyrene, 2-(methacryloyloxy)ethyl trimethylammonium chloride, 4-styrenesulfonic acid sodium and N,N'-dimethyl-(methylmethacryloyl ethyl) ammonium propanesulfonate, respectively. The functionalized surfaces had different efficacies in preventing adsorption of bovine serum albumin (BSA), adhesion of the Gram-negative bacterium Pseudomonas sp. NCIMB 2021 and the Gram-positive Staphylococcus aureus, and settlement of cyprids of the barnacle Amphibalanus amphitrite (=Balanus amphitrite). The nonionic hydrophilic, anionic and zwitterionic polymer brushes resisted BSA adsorption during a 2 h exposure period. The nonionic hydrophilic, cationic and zwitterionic brushes exhibited resistance to bacterial fouling (24 h exposure) and cyprid settlement (24 and 48 h incubation). The hydrophobic brushes moderately reduced protein adsorption, and bacteria and cyprid settlement. The anionic brushes were least effective in preventing attachment of bacteria and barnacle cyprids. Thus, the best approach to combat biofouling involves a combination of nonionic hydrophilic and zwitterionic polymer brush coatings on material surfaces. PMID:22963034

Yang, Wen Jing; Neoh, Koon-Gee; Kang, En-Tang; Lee, Serina Siew Chen; Teo, Serena Lay-Ming; Rittschof, Daniel

2012-01-01

149

Synthesis of polyphenylacetylene by radiation-induced polymerization in deoxycholic acid clathrate  

NASA Astrophysics Data System (ADS)

Phenylacetylene was polymerized as inclusion compound (clathrate) inside deoxycholic acid (DOCA) crystals. The polymerization was initiated by ? radiation and a total dose of 320 kGy was employed. The resulting polyphenylacetylene (PPA) was isolated by dissolution of deoxycholic acid in boiling ethanol. PPA high polymer was accompanied by a series of phenylacetylene oligomers, which were detected by liquid chromatographic analysis (HPLC). PPA was characterized by electronic absorption spectroscopy and by FT-IR spectroscopy in comparison to a reference PPA prepared by a stereospecific catalyst. The microstructure of PPA from inclusion polymerization was highly trans type, similar to that observed on PPA prepared by bulk radiolysis. No optical activity was detected by polarimetry on PPA prepared by inclusion polymerization. The host-guest complex PPA/DOCA was studied by differential thermal analysis (DTA) and by thermogravimetry (TGA). DTA provided evidences of the host-guest complex formation from the shift of the melting point of DOCA while the TGA confirmed the identity - in terms of thermal behaviour - of the PPA from inclusion polymerization with that from stereospecific polymerization.

Cataldo, Franco; Strazzulla, Giovanni; Iglesias-Groth, Susana

2009-04-01

150

Real time in situ spectroscopic characterization of radiation induced cationic polymerization of glycidyl ethers  

NASA Astrophysics Data System (ADS)

Radiation curable polymeric materials suffer from relatively poor mechanical properties. Moreover, the curing behavior of such systems (i.e. the exact relationship between chemical kinetics and key processing variables) is not fully understood. In order to design improved epoxy based electron beam (EB) curable systems, and in order to develop appropriate process models, a detailed knowledge of the kinetics of epoxy cationic polymerization induced by ultraviolet (UV) or EB irradiation is required. In this work, we present our development of a technique based on real time near infrared (RTIR) spectroscopy for performing in situ kinetic analysis of radiation induced cationic polymerization of epoxy systems. To our knowledge this is the first time such data have been collected and presented for high-energy EB (10 MeV) induced polymerization. A demonstration of the technique for deterministic evaluation of degree of cure is shown using model glycidyl ether (phenyl glycidyl ether and diglycidyl ether of bisphenol A) resins and isothermal curing conditions. The impact of initiation rate on polymerizations with UV and EB for the cationic initiator is directly evident by comparative analysis. The sensitivity of the RTIR method and ability to produce quantitative data evidence of reaction mechanisms is demonstrated. The type of data presented in this work forms the basis for cure models being developed.

Mascioni, Matteo; Sands, James M.; Palmese, Giuseppe R.

2003-08-01

151

On the mechanism of radiation-induced polymerization of vinyl monomers in ionic liquid  

NASA Astrophysics Data System (ADS)

An attempt was made to investigate the mechanism controlling the radiation-induced polymerization of vinyl monomers in room temperature ionic liquids. For that purpose, copolymerization of styrene (St) and methyl methacrylate (MMA) was initiated by 60Co gamma radiation in a moisture-stable ionic liquid, [choline chloride][ZnCl2], and its mixture with THF (4:1 v/v). By analyzing the product composition with FTIR for a series of poly(St-co-MMA) samples, it was found that the mole fraction of St in the copolymer is linearly proportional to the mole fraction of St in the feed. Therefore, radiation polymerization in ionic liquid and its mixture with organic solvent is suggested to be a radical propagating process.

Liu, Yaodong; Wu, Guozhong

2005-06-01

152

Subacute radiation dermatitis: a histologic imitator of acute cutaneous graft-versus-host disease  

SciTech Connect

The histopathologic changes of radiation dermatitis have been classified either as early effects (necrotic keratinocytes, fibrin thrombi, and hemorrhage) or as late effects (vacuolar changes at the dermal-epidermal junction, atypical radiation fibroblasts, and fibrosis). Two patients, one exposed to radiation therapeutically and one accidentally, are described. Skin biopsy specimens showed an interface dermatitis characterized by numerous dyskeratotic epidermal cells with lymphocytes in close apposition (satellite cell necrosis); that is, the epidermal changes were similar to those in acute graft-versus-host disease. Because recipients of bone marrow transplants frequently receive total body irradiation as part of their preparatory regimen, the ability of radiation to cause persistent epidermal changes similar to those in acute graft-versus-host disease could complicate the interpretation of posttransplant skin biopsy specimens.

LeBoit, P.E.

1989-02-01

153

Achieving highly effective non-biofouling performance for polypropylene membranes modified by UV-induced surface graft polymerization of two oppositely charged monomers.  

PubMed

A major problem in membrane technology for applications such as wastewater treatment or desalination is often the loss of membrane permeability due to biofouling initiated from protein adsorption and biofilm formation on the membrane surface. In this study, we developed a relatively simple and yet versatile approach to prepare polypropylene (PP) membrane with highly effective non-biofouling performance. Copolymer brushes were grafted to the surface of PP membrane through UV-induced polymerization of two oppositely charged monomers, i.e., [2-(methacryloyloxy)ethyl]trimethylammonium chloride (TM) and 3-sulfopropyl methacrylate potassium salt (SA), with varying TM:SA molar ratios. Surface analysis with scanning electron microscope (SEM) clearly showed the grafted copolymer brushes on the membrane surfaces and that with X-ray photoelectron spectroscope (XPS) revealed a similar TM:SA ratio of the grafted copolymer brushes to that of the monomer solution used for the polymerization. Water contact angle measurements indicated that the hydrophilicity of the membrane surfaces was remarkably improved by the grafting of the TM/SA copolymer brushes, with the lowest water contact angle of 27 degrees being achieved at the TM:SA ratio of around 1:1. Experiments for antiprotein adsorption with bovine serum album (BSA) and lysozyme (LYZ) and antibiofilm formation with Escherichia coli (E. coli) demonstrated a great dependence of the membrane performance on the TM:SA ratios of the grafted copolymer brushes. It was found that the characteristics of the surface charges of the membrane surfaces played a very important role in the non-biofouling performance, and the membrane surface with balanced positive and negative charges showed the best non-biofouling performance for the proteins and bacteria tested in this study. PMID:20121056

Zhao, Yong-Hong; Zhu, Xiao-Ying; Wee, Kin-Ho; Bai, Renbi

2010-02-25

154

Stability of SG1 nitroxide towards unprotected sugar and lithium salts: a preamble to cellulose modification by nitroxide-mediated graft polymerization.  

PubMed

The range of applications of cellulose, a glucose-based polysaccharide, is limited by its inherently poor mechanical properties. The grafting of synthetic polymer chains by, for example, a "grafting from" process may provide the means to broaden the range of applications. The nitroxide-mediated polymerization (NMP) method is a technique of choice to control the length, the composition and the architecture of the grafted copolymers. Nevertheless, cellulose is difficult to solubilize in organic media because of inter- and intramolecular hydrogen bonds. One possibility to circumvent this limitation is to solubilize cellulose in N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMA) with 5 to 10 wt % of lithium salts (LiCl or LiBr), and carry out grafted polymerization in this medium. The stability of nitroxides such as SG1 has not been studied under these conditions yet, even though these parameters are of crucial importance to perform the graft modification of polysaccharide by NMP. The aim of this work is to offer a model study of the stability of the SG1 nitroxide in organic media in the presence of unprotected glucose or cellobiose (used as a model of cellulose) and in the presence of lithium salts (LiBr or LiCl) in DMF or DMA. Contrary to TEMPO, SG1 proved to be stable in the presence of unprotected sugar, even with an excess of 100 molar equivalents of glucose. On the other hand, lithium salts in DMF or DMA clearly degrade SG1 nitroxide as proven by electron-spin resonance measurements. The instability of SG1 in these lithium-containing solvents may be explained by the acidification of the medium by the hydrolysis of DMA in the presence of LiCl. This, in turn, enables the disproportionation of the SG1 nitroxide into an unstable hydroxylamine and an oxoammonium ion. Once the conditions to perform an SG1-based nitroxide-mediated graft polymerization from cellobiose have been established, the next stage of this work will be the modification of cellulose and cellulose derivatives by NMP. PMID:23946859

Moreira, Guillaume; Charles, Laurence; Major, Mohamed; Vacandio, Florence; Guillaneuf, Yohann; Lefay, Catherine; Gigmes, Didier

2013-08-06

155

Time resolved study of the high energy radiation initiated polymerization  

NASA Astrophysics Data System (ADS)

The EB (electron beam) initiated polymerization of ethyl acrylate (EA) and ethyl methacrylate (EMA) in dilute cyclohexane solution was studied by pulse radiolysis technique with transient spectroscopic detection. The maximum in the absorption spectrum of the intermediates lies at ? = 290-320 nm in EA solution and at ? = 285 in EMA solution. The extinction coefficients of the intermediates at the maximum of the spectrum were calculated to be ?285nm ~700 mol-1 dm3 cm-1 in EMA solution and ?290-320nm ~300 mol-1 dm3 cm-1 in EA solution. From the decay curves rate parameters of cm termination (2kt) were calculated. The decays were generally found to be second order with a rate coefficient of 1.4×109 mol-1 dm3 s-1 in EMA solutions and 6×108 mol-1 dm3 s-1 in EA solutions. In some cases deviation from a single second order was observed. This was interpreted in terms of the hindered mobility of the growing radicals.

Takács, E.; Wojnárovits, L.

1995-11-01

156

Radiation-Induced Polymerization and Other Reactions of n-Perfluoropentadiene-1,4 at High Temperature and Pressure.  

National Technical Information Service (NTIS)

The radiation-induced polymerization of n-perfluoropentadiene-1,4 was studied at temperatures of 100-170C. and pressures of 8,000-15,000 atm. Kinetic evidence indicates that polymerization occurs by a free radical reaction; the activation energy is betwee...

D. W. Brown J. E. Fearn R. E. Lowry

1964-01-01

157

Biocompatibility of polypropylene non-woven fabric membrane via UV-induced graft polymerization of 2-acrylamido-2-methylpropane sulfonic acid  

NASA Astrophysics Data System (ADS)

This work described the graft polymerization of a sulfonic acid terminated monomer, 2-acrylamido-2-methylpropane sulfonic acid (AMPS), onto the surface of polypropylene non-woven (NWF PP) membrane by O 2 plasma pretreatment and UV-induced photografting method. The chemical structure and composition of the modified surfaces were analyzed by FTIR-ATR and XPS, respectively. The wettability was investigated by water contact angle and equilibrium water adsorption. And the biocompatibility of the modified NWF PP membranes was evaluated by protein adsorption and platelet adhesion. It was found that the graft density increased with prolonging UV irradiation time and increasing AMPS concentration; the water contact angles of the membranes decreased from 124° to 26° with the increasing grafting density of poly(AMPS) from 0 to 884.2 ?g cm -2, while the equilibrium water adsorption raised from 5 wt% to 75 wt%; the protein absorption was effectively suppressed with the introduction of poly(AMPS) even at the low grafting density (132.4 ?g cm -2); the number of platelets adhering to the modified membrane was dramatically reduced when compared with that on its virgin surface. These results indicated that surface modification of NWF PP membrane with AMPS was a facile approach to construct biocompatible surface.

Song, Lingjie; Zhao, Jie; Yang, Huawei; Jin, Jing; Li, Xiaomeng; Stagnaro, Paola; Yin, Jinghua

2011-10-01

158

Radiation-induced grafting of N-isopropylacrylamide and acrylic acid onto polypropylene films by two step method  

NASA Astrophysics Data System (ADS)

Binary graft copolymerization of pH sensitive acrylic acid (AAc) and thermosensitive N-isopropylacrylamide (NIPAAm) monomers onto pre-irradiated polypropylene films (PP) was carried out by two individual steps using a Co60 gamma radiation source. The influence of preparation conditions, such as pre-irradiation dose and reaction time on grafting yield was studied. The swelling behavior and FTIR-ATR study for PP films grafted films were investigated.

Ramírez-Fuentes, Yessica S.; Bucio, Emilio; Burillo, Guillermina

2007-12-01

159

Specialty polymeric membranes. 8: Separation of benzene from benzene/cyclohexane mixtures with nylon 6-graft-poly(butyl methacrylate) membranes  

SciTech Connect

A novel pervaporation membrane was prepared by radical graft polymerization of butyl methacrylate onto nylon 6. The permselectivity toward benzene was increased by the introduction of poly(butyl methacrylate) onto a nylon 6 membrane. From pervaporation and sorption experiments, it was shown that the introduction of poly(butyl methacrylate) onto a nylon 6 membrane leads to the enhancement of permselectivity toward benzene. The solubility data for benzene were described by a combination of simple sorption and specific sorption, while cyclohexane solubility was described by simple sorption.

Yoshikawa, Masakazu; Tsubouchi, Keisuke; Kitao, Toshio [Kyoto Inst. of Tech., Matsugasaki, Kyoto (Japan). Dept. of Polymer Science and Engineering

1999-02-01

160

Platelet adhesion and protein adsorption on silicone rubber surface by ozone-induced grafted polymerization with carboxybetaine monomer.  

PubMed

Platelet adhesion and protein adsorption on the silicone rubber film grafted with N,N'-dimethyl-N-methacryloyloxyethyl-N-(2-carboxyethyl) ammonium (DMMCA) was studied. The grafting was carried out by means of ozone-induced method and was confirmed by ATR-FTIR and XPS investigations. The grafted films possessed relatively hydrophilic surface revealed by contact angle measurement. The blood compatibility of the grafted film was evaluated in vitro by platelet adhesion in platelet-rich plasma (PRP) and protein absorption in bovine fibrinogen (BFG) using silicone film as the reference. No substantial platelet adhesion was observed for the grafted films incubated in PRP for 60 and 180 min. The protein absorption was also significantly reduced after incubated in bovine fibrinogen for 60 min. Both the results indicated that the blood compatibility of silicone rubber was greatly improved by ozone-induced grafting of carboxybetaine zwitterionic polymer onto its surface. PMID:15698757

Zhou, Jun; Yuan, Jiang; Zang, Xiaopeng; Shen, Jian; Lin, Sicong

2005-03-10

161

New polymeric gel electrolytes consisting of oligo(ethylene oxide)-grafted polymethacrylate matrices for rechargeable lithium batteries  

Microsoft Academic Search

Lithium ion conductors with novel polymeric matrices have been developed for rechargeable lithium batteries operating at ambient temperature. The polymeric electrolytes were prepared by photo-induced radical co-polymerization of mixtures of ethylmethacryl-methyl carbonate (EMMC) and diethyleneglycol dimethacrylate (DEGDM) dissolving LiClO4 with propylene carbonate (PC) as plasticizing solvent. The resulting composite films were homogeneous, flexible and self-standing. The ionic conductivity depended much

Masayuki Morita; Masashi Ishikawa; Katsushi Asanomi

1998-01-01

162

Cell sheet engineering: solvent effect on nanometric grafting of poly-n-isopropylacrylamide onto polystyrene substrate under ultraviolet radiation  

PubMed Central

Background: The best solvent type and ratio for grafting of poly-n-isopropylacrylamide (PNIPAAm) on the surface of polystyrene is obtained under ultraviolet radiation. In this study, the effects of solvents, such as water, methanol, and their combinations, under ultraviolet radiation were investigated successfully. Method and results: Attenuated total reflection Fourier transform infrared analysis showed the existence of the graft PNIPAAm on the substrate for all samples resolved in solvents. The best solvent ratio and NIPAAm concentration for grafting was obtained with 40% NIPAAm concentrations resolved in a solvent of 9:1 (v/v) water/methanol (120%). Scanning electron microscopic and atomic force microscopic images clearly showed that a 10% increase of methanol to water would increase the amount of grafting. Surface topography and graft thickness in atomic force microscopic images of the grafted samples showed that the thickness of these grafts was about 600 nm. The drop water contact angles of the best grafted sample at 37°C and 4°C were 43.3° and 60.4°, respectively, which demonstrated the hydrophilicity and hydrophobicity of the grafted surfaces. Differential scanning calorimetric analysis also revealed the low critical solution temperature of the grafted sample to be 32°C. Thermoresponsive polymers were grafted to dishes covalently, which allowed epithelial cells to attach and proliferate at 37°C. The cells were also detached spontaneously without using enzymes when the temperature dropped below 4°C. Conclusion: MTT analysis also showed good viability of cells on the grafted samples, suggesting that this type of grafted material had potential as a biomaterial for cell sheet engineering.

Biazar, Esmaeil; Khorasani, MT; Daliri, M

2011-01-01

163

An investigation of the potential for chemical modification and subsequent polymeric grafting as a means of protecting wood against photodegradation  

Microsoft Academic Search

Pine sapwood samples were chemically modified with methacrylic anhydride, and the modified samples were grafted with styrene via a free radical process. Unmodified, modified, and modified and styrene grafted samples were exposed to UV irradiation and the samples were then analysed for colour, brightness, and chemical changes (using infra-red and X-ray photoelectron spectroscopy). Although modification did impart colour stability to

Callum A. S Hill; Nihat S Cetin; Richard F Quinney; Hilary Derbyshire; Richard J Ewen

2001-01-01

164

Preparation of Modified Chitosan by Graft Polymerization and its Adsorption of Cd2+ and Co2+ from Binary Solution  

NASA Astrophysics Data System (ADS)

The grafting copolymerization of chitosan with acrylamide and acrylonitrile was studied which initiated by NaHSO3-K2S2O8. And the chitosan-acrylamide-acrylonitrile ternary graft copolymer was synthesized in N2 atmosphere. Under the optimal experimental conditions, the average graft ratio and the graft efficiency could up to 852.46% and 85.26%, respectively. The adsorption selectivity and influences to the adsorption by factors like adsorption time, adsorption temperature, initial concentration of metal ion and initial pH of the solution were studied. The results showed that: the adsorption selectivity was obtained of the ternary graft copolymer to Cd2+; under the same experimental conditions, the maximum difference of adsorption rate between Cd2+ and Co2+ by polymer would be 31.07%.

Bi, Qiang; Xue, Juanqin; Guo, Yingjuan; Mao, Weibo; Wang, Yujie

2013-07-01

165

Swelling characteristics of konjac glucomannan superabsobent synthesized by radiation-induced graft copolymerization  

NASA Astrophysics Data System (ADS)

Graft copolymerization of konjac glucomannan (KGM) and acrylic acid was induced by 60Co-? irradiation at room temperature. The effects of radiation dose and monomer-to-KGM ratio on grafting yield and equilibrium water absorbency were investigated. The KGM-based superabsorbent polymer (KSAP) could absorb water 625 times of its dry weight when the radiation dose was 5.0 kGy and monomer-to-KGM ratio was 5. The structure of KSAP was characterized by FTIR, XRD, and SEM. KSAP showed a lower crystallinity than KGM. The porous microstructure of KSAP was revealed by SEM. The diffusion mechanism of water in the hydrogel is consistent with the anomalous diffusion model. Cations, especially multivalent cations, greatly reduced water absorbency of KSAP. Rising temperature, acidic or basic solutions are not favorable for the swelling of KSAP.

Wu, Jia; Deng, Xiao; Lin, Xiangyang

2013-02-01

166

Surface modification of nanofiltration membranes to improve the removal of organic micro-pollutants (EDCs and PhACs) in drinking water treatment: Graft polymerization and cross-linking followed by functional group substitution  

Microsoft Academic Search

A commercially available thin film composite (TFC) polyamide (PA) nanofiltration (NF) membrane was chemically modified to improve its rejection capacity for selected organic micro-pollutants categorized as endocrine disrupting chemicals (EDCs) and pharmaceutically active compounds (PhACs): bisphenol-A (BPA), ibuprofen, and salicylic acid. The raw NF membrane was altered using the following modification sequence: graft polymerization (methacrylic acid (MA)-membrane); cross-linking of grafted

Jae-Hyuk Kim; Pyung-Kyu Park; Chung-Hak Lee; Heock-Hoi Kwon

2008-01-01

167

Photo-induced living\\/controlled surface radical grafting polymerization and its application in fabricating 3-D micro-architectures on the surface of flat\\/particulate organic substrates  

Microsoft Academic Search

This feature article covers the fundamental chemistry and applications of photo-induced living surface grafting polymerization. The mechanism of activation of inert alkyl C–H bonds of polymer substrates, the structures of the active free radical and reversible dormant species, the modes of the grafting chain growth (including linear, branched and cross-linked variants), and the role of spatial effect are discussed. Two

Yuhong Ma; Lianying Liu; Wantai Yang

2011-01-01

168

Radiation-induced grafting of vinylbenzyltrimethylammonium chloride (VBT) onto cotton fabric and study of its anti-bacterial activities  

NASA Astrophysics Data System (ADS)

Mutual radiation grafting technique using 60Co gamma radiation has been used to carry out grafting of vinylbenzyltrimethylammonium chloride (VBT) onto cotton cellulose substrate. Grafting yield increased with radiation dose and decreased with dose rate but was adversely affected by the presence of O2 and salts of Fe2+ and Cu2+. However, the presence of an acid did not affect grafting in the concentration range studied. The effect of organic solvents like methanol, ethanol, n-propanol, iso-propanol, tert-butanol on grafting yield was investigated in the mixed aqueous solvent system. The VBT grafted cotton samples showed significantly higher water uptake and water retention properties and possessed excellent anti-bacterial activity against strains like Escherichia coli and Staphylococcus aureus. Samples with 25% grafting extent showed 6 log cycles reduction in bacterial counts within 6 h of exposure time. The anti-bacterial activity of the grafted cotton samples was retained after several cycles of washing and drying in a commercial detergent powder.

Kumar, Virendra; Bhardwaj, Y. K.; Rawat, K. P.; Sabharwal, S.

2005-06-01

169

Asymmetric radiation-induced inclusion polymerization of 3-methyl-1,4-pentadiene in deoxycholic acid  

NASA Astrophysics Data System (ADS)

The radiation-induced polymerization of 3-methyl-1,3-pentadiene (3MPD) as an inclusion complex in deoxycholic acid (DOCA) has produced in good yield the optically active polymer poly(3-methyl-1,4-pentadiene) (P3MPD) whose structure and properties were studied by FT-IR spectroscopy and thermal analysis (TGA, DTG and DTA). The data show that the polymer is essentially trans-1,4-P3MPD as expected for the polymerization in constrained media. Trans-1,4-P3MPD is optically active with [?]D values comprised between +4.3 and +5.6. The optical rotatory dispersion curve of the P3MPD is completely different from that of DOCA as expected.

Cataldo, Franco; Ursini, Ornella; Angelini, Giancarlo

2010-01-01

170

Synthesis and characterization of ?-CD-coated polystyrene microspheres by ?-ray radiation emulsion polymerization.  

PubMed

Polystyrene (PS) microspheres coated with ?-cyclodextrin (?-CD) were fabricated via ?-ray-induced emulsion polymerization in a ternary system of styrene/?-CD/water (St/?-CD/water). The solid inclusion complex of St and ?-CD particles formed at the St droplets-water interface can stabilize the emulsion as the surfactant. TEM and XPS results showed that ?-CD remains on the surface of PS particles. The average size of the PS particles increases from 186 to 294 nm as the weight ratio of ?-CD to St rises from 5% to 12.5%. The water contact angle (CA) of PS latex film is lower than 90°, and reduces with the ?-CD content even to 36°. Thus, this work provides a new and one-pot strategy to surface hydrophilic modification on hydrophobic polymer particles with cyclodextrins through radiation emulsion polymerization. PMID:22887797

Xu, Dezhi; Wang, Mozhen; Ge, Xuewu; Lam, Michael Hon-Wah

2012-08-10

171

The role of partitioning of reagents in grafting and curing reactions initiated by ionizing radiation and UV  

NASA Astrophysics Data System (ADS)

Experimental evidence involving monomer absorption studies using tritiated styrene is shown to support the proposal that additives such as mineral acids and certain inorganic salts when dissolved in the monomer solution enhance radiation grafting yields by a mechanism involving partitioning of reagents. Photoinitiators such as benzoin ethyl ether and its methyl analogue are reported as new additives for grafting of styrene in methanol to cellulose and polypropylene initiated by ionizing radiation. The partitioning concept is shown to be relevant in analogous UV grafting and curing processes.

Chaplin, R. P.; Dworjanyn, P. A.; Gamage, N. J. W.; Garnett, J. L.; Jankiewicz, S. V.; Khan, M. A.; Sangster, D. F.

1996-03-01

172

Grafting N-Isopropyl Acrylamide) from Poly(vinylidene Fluoride) Mirofiltration, Membranes via Direct Surface-Initiated Atom Transfer Radical Polymerization, and Temperature Sensitivity  

NASA Astrophysics Data System (ADS)

Well-defined poly(N-isopropyl acrylamide) (PNIPAAm) brushes on commercial hydrophobic poly(vinylidene fluoride) (PVDF) microfiltration membrane surfaces were prepared, via direct atom transfer radical polymerization (ATRP) with the secondary fluorinated site of PVDF as initiator and water as solvent at 80°C. The effect of solvents on the ATRP was studied in detail. The water as reaction solvent was in favor of surface-initiated ATRP of N-isopropyl acrylamide (NIPAAm) from secondary fluoride of PVDF membranes. The chemical composition and structure of the modified PVDF membrane surfaces were determined by attenuated total reflectance (ATR) Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The surface and cross-section morphology of membranes were studied by scanning electron microscopy (SEM). The pore sizes of the pristine PVDF membrane and the PNIPAAm-grafted PVDF membranes were measured using micro-image analysis and process software. The introduction of the well-defined PNIPAAm on the PVDF membrane gave rise to hydrophilicity. Water contact angles of PVDF membranes reduced after the surface grafting of PNIPAAm. Water fluxes and protein solution permeation experiments revealed that the PNIPAAm-grafted PVDF membranes exhibited temperature-responsive permeability. The unique microstructure of PNIPAAm brushes facilitated hydrophilicity below the lower critical solution temperature.

Chen, Yiwang; Xiao, Jichun; Zhou, Weihua; Deng, Qilan; Nie, Huarong; Wan, Meixiang; Bai, Fenglian

173

Synthesis and characterization of thermo- and pH- sensitive hydrogels based on Chitosan-grafted N-isopropylacrylamide via ?-radiation  

NASA Astrophysics Data System (ADS)

Thermo- and pH-sensitive hydrogels were prepared by graft copolymerization of chitosan (CS) and N-isopropylacrylamide via ?-radiation. The effects of monomer concentration and irradiation dose on grafting percentage and grafting efficiency were studied. The graft copolymers were characterized by 13C CP/MAS NMR and thermogravimetric analysis. The pH and thermosensitivity and swelling properties of the hydrogels were investigated. The results showed that the grafting percentage and grafting efficiency increased with the increase of monomer concentration and total irradiation dose. The highest grafting percentage is 620%, the lower critical solution temperature (LCST) of this hydrogel is about 28 °C.

Cai, Hong; Zhang, Zheng Pu; Chuan Sun, Ping; Lin He, Bing; Xia Zhu, Xiao

2005-09-01

174

A novel preparation of surface-modified paramagnetic magnetite/polystyrene nanocomposite microspheres by radiation-induced miniemulsion polymerization.  

PubMed

A novel and facile approach to the preparation of paramagnetic magnetite/polystyrene nanocomposite microspheres by 60Co gamma-ray radiation-induced miniemulsion polymerization is reported. First, we modified the magnetite nanoparticles (MPs) with a Y-shaped surfactant: 12-hexanoyloxy-9-octadecenoic acid (HOA). Nanocomposite microspheres consisting of polystyrene-iron oxide nanoparticles then were prepared by the radiation-induced miniemulsion polymerization of styrene in the presence of HOA-modified MPs using HOA as stabilizer. The final products were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field-emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The effects of the dose rate, the amounts of added hexadecane (HD) and MPs, and the morphology of the final products were studied. We have also studied the polymerization kinetics to prove the miniemulsion polymerization mechanism of the nanocomposite microspheres. PMID:18804782

Qian, Zhen; Zhang, Zhicheng; Chen, Yun

2008-09-19

175

Adhesion of Gibberella fujikuroi cells on surfaces of carriers by radiation polymerization  

NASA Astrophysics Data System (ADS)

The adhesion of Gibberella fujikuroi cells on the covered polymers which were prepared by radiation polymerization technique was investigated. The adhesion of the cells was related to the surface free energy and polar component force. The copolymer resulted from hydrophillic and hydrophobic monomer and porous structure were favorable to the adhesion of the cells. However, the anionic poly-acrylic acid was not unfavorable to the adhesion of the cells. The adhesion process of the cells on the carrier covered with copolymer was observed by scanning electron microscopy.

Lu, Zhaoxin; Xie, Zongchuan; Kumkura, Minoru

1995-09-01

176

Comparative study of grafting a polyampholyte in a fluoropolymer membrane by gamma radiation in one or two-steps  

NASA Astrophysics Data System (ADS)

Binary graft copolymerization of pH-sensitive monomers (N,N-dimethylaminoethyl methacrylate, (DMAEMA) and acrylic acid (AAc) onto polyvinylidene fluoride (PVDF) membranes with pore sizes of 0.22 and 0.45 ?m was conducted by one and two-steps grafting using a 60Co gamma radiation source (Gammabeam 651 PT). The DMAEMA and AAc monomers were grafted by an oxidative pre-irradiation method in one-step grafting to obtain PDVF-g-(DMAEMA-co-AAc), and both direct irradiation and an oxidative pre-irradiation method were used to obtain the graft copolymer (PVDF-g-DMAEMA)-g-AAc in two-steps grafting. The optimal conditions, such as reaction time, temperature, solvent, monomer concentration and dose, were studied, the aim of this work was to investigate how these factors affecting the graft percent of DMAEMA and AAc prepared in one and two-steps grafting and their structural differences and also characterize the grafting membrane through analytical techniques.

Estrada-Villegas, G. M.; Bucio, E.

2013-11-01

177

Radiation-induced polymerization monitored in situ by time-resolved fluorescence of probe molecules in methyl methacrylate  

NASA Astrophysics Data System (ADS)

A technique is presented for monitoring radiation-induced polymerizations in situ based on the measurement of the fluorescence lifetime of molecular probes dissolved in the polymerizing medium. This method is illustrated with results on methyl methacrylate (MMA) using two fluorogenic probe molecules; N-(2-anthracene)methacrylamide (AnMA) and maleimido-fluoroprobe (MFP), a molecule which has a highly dipolar excited state.

Frahn, Mark S.; Abellon, Ruben D.; Luthjens, Leonard H.; Vermeulen, Martien J. W.; Warman, John M.

2003-08-01

178

Grafting of methyl methacrylate to cellulose and polypropylene with UV and ionising radiation in the presence of additives including CT complexes  

NASA Astrophysics Data System (ADS)

Detailed studies of the grafting of polar methyl methacrylate (MMA) to two representative backbone polymers, cellulose and polypropylene (PPE) in the presence of additives, using ionising radiation and UV as initiating sources, are reported. The results are compared with analogous grafting work with non polar styrene previously studied. The additives chosen for examination were predominantly components used in radiation curing formulations since grafting and curing are known to be mechanistically related. The additives were mineral acid, photoinitiators, vinyl ethers, oligomers, polyfunctional monomers including multifunctional acrylates (MFAs) and methacrylates (MFMAs). For the first time charge transfer (CT) monomer complexes have been used as additives in the current work. The CT complexes themselves, being monomers, have also been directly radiation grafted to cellulose. Mechanisms for the above grafting processes are proposed. The significance of this grafting work in analogous radiation curing is discussed. The grafting of the CT complexes, themselves, is shown to lead to new copolymers with potential industrial applications.

Garnett, J. L.; Ng, L.-T.; Viengkhou, V.

1999-10-01

179

Radiation grafted and sulfonated (FEP-g-polysterene) - An alternative to perfluorinated membranes for PEM fuel cells?  

NASA Astrophysics Data System (ADS)

Partially fluorinated proton exchange membranes (PEMs) were synthesized for fuel cell applications by simultaneous radiation grafting of styrene on FEP films followed by sulfonation. Properties of the synthesized membranes can be tailored by varying the degree of grafting and crosslinking. The performance of these membranes was tested in H2/O2 fuel cells. Long time testing showed steady performance for high grafted membranes over periods of more than 300 h at a cell temperature of 60 C. Low grafted membranes and the Morgane CDS membrane showed considerable decay of cell power on the same time scale. A fast degradation of all membranes occurred at a cell temperature of 80 C. It is noted that grafting in film form makes this process a potentially cheap and easy technique for the preparation of solid polymer fuel cell electrolytes.

Buechi, F. N.; Gupta, B.; Rouilly, M.; Hauser, P. C.; Chapiro, A.; Scherer, G. G.

180

Synthesis of poly(N-isopropylacrylamide) hydrogels by radiation polymerization and cross-linking  

SciTech Connect

Poly(N-isopropylacrylamide) [poly(NIPAAm)] shows a typical thermal reversibility of phase transition in aqueous solutions. That is, it precipitates from solution above a critical temperature called the lower critical solution temperature (LCST) and dissolves below this temperature. When it is cross-linked, the obtained hydrogel collapses above LCST, while it swells and expands below LCST. This hydrogel has received much attention recently and has been used as a model system to demonstrate the validity of theories describing the coil-globule transition, swelling of networks, and folding and unfolding of biopolymers. It has also been proposed for various applications ranging from controlled drug delivery to solute separation. Poly(NIPAAm) hydrogel is usually synthesized at room temperature from an aqueous solution of the monomer by using a redox initiator composed of ammonium persulfate and N,N,N{prime},N{prime}-tetramethylethylenediamine in the presence of N,N{prime}-methylenebisacrylamide as a cross-linker. Since the LCST of poly(NIPAAm) is around 32 C, the polymerization at room temperature proceeds in a homogeneous solution. Recently, poly(NIPAAm) hydrogels were synthesized by starting the polymerization below the LCST and then elevating the temperature above it, by which method macroporous gels with fast temperature response were obtained. The idea is to apply a radiation--induced polymerization method for the synthesis of poly(NIPAAm) hydrogels. This method offers unique advantages for synthesis: it is a simple and additive-free process at all temperatures, and the degree of cross-linking can be easily controlled by irradiation conditions. Therefore, radiation methods are especially attractive for the synthesis of hydrogels with potential biomedical application where the residual chemical initiators may contaminate the product. It is possible to combine into one step the synthesis and sterilization of the product, and it is economically competitive.

Nagaoka, Noriyasu; Kubota, Hitoshi; Katakai, Ryoichi [Gunma Univ. (Japan). Dept. of Chemistry; Safranj, Agneza; Yoshida, Masaru; Omichi, Hideki [Japan Atomic Energy Research Inst., Gunma (Japan). Dept. of Material Development

1993-12-20

181

Radiation induced graft copolymerization of n-butyl acrylate onto poly(ethylene terephthalate) (PET) films and thermal properties of the obtained graft copolymer  

NASA Astrophysics Data System (ADS)

n-Butyl acrylate (BA) was successfully grafted onto poly(ethylene terephthalate) (PET) film using simultaneous radiation induced graft copolymerization with gamma rays. When BA concentration ranges from 20% to 30%, the Degree of Grafting (DG), measured by gravimetry and 1H NMR, increases with the monomer concentration and absorbed dose, but decreases with dose rate from 0.83 to 2.53 kGy/h. The maximum DG can reach up to 22.1%. The thermal transition temperatures such as glass-transition temperature (Tg) and cold-crystallization temperature (Tcc) of PET in grafted films were little different from those in original PET film, indicating that microphase separation occurred between PBA side chains and PET backbone. This work implied that if PET/elastomers (e.g., acrylate rubber) blends are radiated by high energy gamma rays under a certain condition, PET-g-polyacrylate copolymer may be produced in-situ, which will improve the compatibility between PET and the elastomers so as to improve the integral mechanical properties of PET based engineering plastic.

Ping, Xiang; Wang, Mozhen; Ge, Xuewu

2011-05-01

182

Free radical generation upon plasma treatment of cotton fibers and their initiation efficiency in surface-graft polymerization  

Microsoft Academic Search

Low-temperature plasma was used to activate mercerized cotton fabrics, to be followed by grafting with various methacrylates. Careful analysis of the experimental electron spin resonance (ESR) lineshapes of cotton samples treated at different RF powers made it possible to recognize and quantify four different species of free radicals still persistent 30 h after irradiation in the samples maintained under inert

Laura Andreozzi; Valter Castelvetro; Gianluca Ciardelli; Leopoldo Corsi; Massimo Faetti; Enrico Fatarella; Fabio Zulli

2005-01-01

183

Radiation-induced grafting of multi-walled carbon nanotubes in glycidyl methacrylate–maleic acid binary aqueous solution  

Microsoft Academic Search

With the aim to improve the compatibility between multi-walled carbon nanotubes (MWCNTs) and nylon-6, purified MWCNTs (p-MWCNTs) were grafted successfully with glycidyl methacrylate–maleic acid in aqueous solution using a single-step radiation method. The chemical structure and morphology of grafted p-MWCNTs (g-MWCNTs) was investigated by micro-FTIR, Raman spectroscopy and transmission electron microscopy. The prepared nylon-6\\/g-MWCNTs composite has higher mechanical strength and

Haibo Yu; Xinyue Mo; Jing Peng; Maolin Zhai; Jiuqiang Li; Genshuan Wei; Xiaohong Zhang; Jinliang Qiao

2008-01-01

184

Poly(2-hydroxyethyl methacrylate) grafted halloysite nanotubes as a molecular host matrix for luminescent ions prepared by surface-initiated RAFT polymerization and coordination chemistry  

NASA Astrophysics Data System (ADS)

A fluorescent nanohybrid complex comprising of halloysite nanotubes (HNTs), poly(2-hydroxyethyl methacrylate) (PHEMA), and europium ions (Eu3+) was synthesized by the combination of surface-initiated reversible addition-fragmentation chain transfer (SI-RAFT) polymerization and coordination chemistry. Initially, PHEMA was grafted from the HNTs by SI-RAFT and then reacted with succinic anhydride to provide carboxyl acid groups on the external layers of HNTs-g-PHEMA nanohybrids. The subsequent coordination of the nanohybrids with Eu3+ ions afforded photoluminescent Eu3+ tagged HNTs-g-PHEMA nanohybrid complexes (HNTs-g-PHEMA-Eu3+). The structure, morphology, and fluorescence properties of the Eu3+ coordinated nanohybrid complexes were investigated by respective physical and spectral studies. FT-IR, XPS, and EDS analyses suggested the formation of the HNTs-g-PHEMA-Eu3+ nanohybrids. FE-SEM images indicated the immobilization of polymer layers on HNTs. TGA scans further demonstrated the grafting of PHEMA onto HNTs surface. The optical properties of HNTs-g-PHEMA-Eu3+ nanohybrid complexes were investigated by photoluminescence spectroscopy.

Islam, Md. Rafiqul; Bach, Long Giang; Lim, Kwon Taek

2013-07-01

185

Synthesis and characterization of thermo- and pH sensitive hydrogels based on Chitosan-grafted N-isopropylacrylamide via gamma-radiation  

Microsoft Academic Search

Thermo- and pH-sensitive hydrogels were prepared by graft copolymerization of chitosan (CS) and N-isopropylacrylamide via gamma-radiation. The effects of monomer concentration and irradiation dose on grafting percentage and grafting efficiency were studied. The graft copolymers were characterized by 13C CP\\/MAS NMR and thermogravimetric analysis. The pH and thermosensitivity and swelling properties of the hydrogels were investigated. The results showed that

Hong Cai; Zheng Pu Zhang; Ping Chuan Sun; Bing Lin He; Xiao Xia Zhu

2005-01-01

186

Synthesis and characterization of thermo- and pH sensitive hydrogels based on Chitosan-grafted N-isopropylacrylamide via ?-radiation  

Microsoft Academic Search

Thermo- and pH-sensitive hydrogels were prepared by graft copolymerization of chitosan (CS) and N-isopropylacrylamide via ?-radiation. The effects of monomer concentration and irradiation dose on grafting percentage and grafting efficiency were studied. The graft copolymers were characterized by 13C CP\\/MAS NMR and thermogravimetric analysis. The pH and thermosensitivity and swelling properties of the hydrogels were investigated. The results showed that

Hong Cai; Zheng Pu Zhang; Ping Chuan Sun; Bing Lin He; Xiao Xia Zhu

2005-01-01

187

POLYMERIZATION INDUCED BY IONIZING RADIATION AT LOW TEMPERATURES. I. EVIDENCE FOR THE SIMULTANEOUS EXISTENCE OF IONIC AND FREE-RADICAL MECHANISMS IN THE POLYMERIZATION OF STYRENE AND 2,4-DIMETHYLSTYRENE  

Microsoft Academic Search

By means of initiation with ionizing radiation, styrene and 2,4-; dimethylstyrene were polymerized in the crystalline solid state, in the pure ; liquid state, and in solution at different temperatures (-80 to 25 deg C). In ; solution polymerization, it was found that for the same type of initiation, other ; conditions being constant, the mechanism by which these monomers

Catherine S. Hsia Chen; Robert F. Stamm

1962-01-01

188

Grafting of PMMA brushes on titania nanoparticulate surface via surface-initiated conventional radical and “controlled” radical polymerization (ATRP)  

Microsoft Academic Search

Stable dispersion of titania nanoparticles in organic solvents are obtained by grafting poly(methyl methacrylate) layer on\\u000a to the surface. Titania nanoparticles are synthesized through the hydrolysis of titanium (IV) isopropoxide. The average size\\u000a of the titania particles is found to be 15 ± 2 nm. The polymer layer was introduced onto the surface by immobilizing the initiating\\u000a moiety. Azo initiator moiety required for

G. K. Raghuraman; Jürgen Rühe; Raghavachari Dhamodharan

2008-01-01

189

Molecularly imprinted polymer membranes for substance-selective solid-phase extraction from water by surface photo-grafting polymerization  

Microsoft Academic Search

Hydrophilized polyvinylidene fluoride microfiltration membranes were surface-modified in the presence of a template (terbumeton) in methanol with a graft copolymer of a functional monomer (2-acrylamido-2-methyl-1-propane sulfonic acid, AMPS, methacrylic acid, MAA, or acrylic acid, AA) and a cross-linker (N,N?-methylene-bis-acrylamide) using UV irradiation and benzophenone as photoinitiator. As result, membranes covered with a thin layer of imprinted polymer selective to terbumeton

Tatiana A Sergeyeva; Heike Matuschewski; Sergiy A Piletsky; Jürgen Bendig; Uwe Schedler; Mathias Ulbricht

2001-01-01

190

Synthesis of palladium nanoparticles in a ceramic matrix using radiation grafting method  

NASA Astrophysics Data System (ADS)

Silicon carbide (SiC) ceramics containing palladium (Pd) nanoparticles were synthesized by the combination of the radiation grafting method, which allowed for uniform dispersion of Pd ions in polycarbosilane (PCS), and subsequent heat treatment, which was used to promote the bleedout phenomenon. The size and distribution of the Pd nanoparticles varied with the heat-treatment temperature. TEM and XRD analyses indicated that Pd nanoparticles of 2-5 nm in size were homogeneously distributed in the SiC ceramic matrix at temperatures lower than 1173 K. At a temperature of 1373 K, the size of these particles was found to increase and a portion of Pd was changed into Pd silicide. The Pd nanoparticles in samples heated at temperatures lower than 1173 K showed catalytic activity for hydrocarbon oxidation, whereas samples treated at 1373 K did not show any catalytic activity. These results suggest that Pd nanoparticles were formed on the SiC matrix at temperatures lower than 1173 K. The bleedout process enables the production of Pd nanoparticles as a combustion catalyst from radiation-grafted Pd-PCS.

Yoshimura, Kimio; Hakoda, Teruyuki; Sugimoto, Masaki; Yamamoto, Shunya; Yoshikawa, Masahito

2011-04-01

191

Grafting of thermoresponsive polymer from the surface of functionalized multiwalled carbon nanotubes via atom transfer radical polymerization  

Microsoft Academic Search

Multiwalled carbon nanotubes were oxidized with concentrated HNO3 and H2SO4 to introduce carboxylic groups onto carbon nanotubes surfaces. The oxidized carbon nanotubes were reacted subsequently with\\u000a thionyl chloride and 2-Hydroxylethyl-2?-bromoisobutyrate, producing MWNT-based macroinitiators, MWNT-Br, for the atom transfer\\u000a radical polymerization of (N-isopropylacrylamide). FTIR, XPS, 1H NMR, Raman and TGA were used to characterize the resulting products and to determine the

GuoYong Xu; Ru Xia; Hu Wang; XiangChun Meng; QingRen Zhu

2008-01-01

192

Novel diblock copolymer-grafted multiwalled carbon nanotubes via a combination of living and controlled\\/living surface polymerizations  

Microsoft Academic Search

Diels Alder cycloaddition reactions were used to functionalize multiwalled carbon nanotubes (MWNTs) with 1-benzocylcobutene-10-phenylethylene (BCB-PE) or 4-hydroxyethylbenzocyclobutene (BCB-EO). The covalent functionalization of the nanotubes with these initiator precursors was verified by FTIR and thermogravimetric analysis (TGA). After appropriate transformations\\/additions, the functionalized MWNTs were used for surface initiated anionic and ring opening polymerizations of ethylene oxide and e-caprolactone (e-CL), respectively. The

Dimitrios Priftis; Georgios Sakellariou; Jimmy W. Mays; Nikos Hadjichristidis

2010-01-01

193

Characterization of Network Structure of Polyacrylamide Based Hydrogels Prepared By Radiation Induced Polymerization  

NASA Astrophysics Data System (ADS)

In this study network structure of polyacrylamide based hydrogels prepared by radiation induced polymerization has been investigated. Polyacrylamide based hydrogels in the rod form were prepared by copolymerization of acrylamide(AAm) with hydroxyl ethyl methacrylate(HEMA) and methyl acrylamide(MAAm) in the presence of cross-linking agent and water by gamma rays at ambient temperature. Molecular weight between cross-links and effective cross-link density of hydrogels were calculated from swelling as well as shear modulus data obtained from compression tests. The results have shown that simple compression analyses can be used for the determination of effective cross-link density of hydrogels without any need to some polymer-solvent based parameters as in the case of swelling based determinations. Diffusion of water into hydrogels was examined by analyzing water absorption kinetics and the effect of network, structure on the diffusion type and coefficient was discussed.

Mahmudi, Naim; ?en, Murat; Güven, Olgun; Rendevski, Stojan

2007-04-01

194

Radiation grafting of acrylic and methacrylic acid to cellulose fibers to impart high water sorbency  

Microsoft Academic Search

Acrylic and methacrylic acids have been directly grafted to rayon and cotton using the preirradiation technique with ⁶° Co gamma rays. The rate of grafting increased with increasing temperature and monomer concentration, as did the final degree of grafting. The amount and rate of grafting also increased with the total irradiation dose but tended to level off at higher doses,

A. H. Zahran; J. L. Williams; V. T. Stannett

1980-01-01

195

Preparation of PTFE-based fuel cell membranes by combining latent track formation technology with graft polymerization  

Microsoft Academic Search

Swift heavy 56MeV 15N3+ ions were generated with particle fluences of 0, 3×106, 3×107, 3×108, 3×109ions\\/cm2 to form a latent track zone in a 25-?m-thick film of polytetrafluoroethylene (iPTFE). Styrene (St) was then grafted onto the iPTFE films by UV-irradiation or pre-?-irradiation, and after sulfonation iPTFE-based proton-conducting membranes were obtained, here called, iPTFE-g(UV)-PStSA and iPTFE-g(?)-PStSA membranes, respectively, which had a

Masaru Yoshida; Yosuke Kimura; Jinhua Chen; Masaharu Asano; Yasunari Maekawa

2009-01-01

196

PDMS-Glass bonding using grafted polymeric adhesive - Alternative process flow for compatibility with patterned biological molecules  

PubMed Central

We report a novel modification of silicone elastomer, polydimethylsiloxane (PDMS) with a polymer graft that allows interfacial bonding between elastomer and glass substrate to be performed without exposure of said substrate to harsh treatment conditions like oxygen plasma. Organic molecules can thus be patterned within microfluidic channels and still remain functional post-bonding. In addition, after polymer grafting the PDMS can be stored in a desiccator for at least 40 days, and activated upon exposure to acidic buffer for bonding. The bonded devices remain fully bonded in excess of 80 psi driving pressure, with no signs of compromise to the bond integrity. Finally, we demonstrate the compatibility of our method with biological molecules using a proof-of-concept DNA sensing device, in which fluorescently-labelled DNA targets are successfully captured by a patterned probe in a device sealed using our method, while the pattern on a plasma-treated device was completely destroyed. Therefore, this method provides a much-needed alternative bonding process for incorporation of biological molecules in microfluidic devices.

Beh, Cyrus Weijie; Zhou, Weizhuang

2013-01-01

197

Preparation of PTFE-based fuel cell membranes by combining latent track formation technology with graft polymerization  

NASA Astrophysics Data System (ADS)

Swift heavy 56 MeV 15N3+ ions were generated with particle fluences of 0, 3×106, 3×107, 3×108, 3×109 ions/cm2 to form a latent track zone in a 25-?m-thick film of polytetrafluoroethylene (iPTFE). Styrene (St) was then grafted onto the iPTFE films by UV-irradiation or pre-?-irradiation, and after sulfonation iPTFE-based proton-conducting membranes were obtained, here called, iPTFE-g(UV)-PStSA and iPTFE-g(?)-PStSA membranes, respectively, which had a straight cylindrical damage zone around the ion path. The degree of grafting was found to be about 7.5% with a particle fluence of 3×107 ions/cm2 and with either the UV-method or the ?-method. The ion-exchange capacity, proton conductivity in the thickness direction, MeOH permeability, tensile strength and elongation at break of the obtained iPTFE-g(UV)-PStSA membrane were 0.50 mmol/g, 0.06 S/cm, 0.15×10-6 cm2/s, 50 MPa and 600%, in contrast to 0.06 mmol/g, 0.06 S/cm, 0.35×10-6 cm2/s, 19 MPa and 210% for the iPTFE-g(?)-PStSA membrane, respectively. In comparison, the Nafion 112 measured in our laboratory exhibited an ion-exchange capacity of 0.91 mmol/g, a proton conductivity of 0.06 S/cm, a MeOH permeability of 1.02×10-6 cm2/s, a tensile strength of 35 MPa and an elongation at break of 295%. It can be concluded from these data that the lower crossover of MeOH, the same proton conductibility, the lower ion-exchange capacity, and the superior mechanical properties of the UV-grafted proton-conducting membranes compared to the Nafion make them promising materials for widespread application in direct methanol fuel cells. On the other hand, the tests of mechanical strength showed that the PTFE base film is subject to degradation by the ion-beam irradiation as well as the ?-irradiation.

Yoshida, Masaru; Kimura, Yosuke; Chen, Jinhua; Asano, Masaharu; Maekawa, Yasunari

2009-12-01

198

Physicochemical aspects of the drugs radiation sterilization in commercial packing (applied scientific problems of radiation pharmaceutical chemistry)  

Microsoft Academic Search

The results of studies on the simultaneous radiosterilization of direct and bifurcational trachea prostheses made of silicon-organic rubber of soft elastic consistency, with polyethylenterephthalate and polyamid cuffs, and radiation chemical grafting of polymeric layer and linking with functional groups of the graft sulfanilamide and antibiotics layer are discussed. Radiopharmaceuticals are also described.

Safarov

1993-01-01

199

Physico-chemical aspects of the drugs radiation sterilization in commercial packing (applied scientific problems of radiation pharmaceutical chemistry)  

SciTech Connect

The results of studies on the simultaneous radiosterilization of direct and bifurcational trachea prostheses made of silicon-organic rubber of soft elastic consistency, with polyethylenterephthalate and polyamid cuffs, and radiation chemical grafting of polymeric layer and linking with functional groups of the graft sulfanilamide and antibiotics layer are discussed. Radiopharmaceuticals are also described.

Safarov, S.A.

1993-12-31

200

Modification of jute yarn by graft-copolymerization with ultraviolet radiation  

NASA Astrophysics Data System (ADS)

A number of formulations was developed with oligomer mixed with functional monomers in the presence of fillers and plasticizer. Then polymers were prepared under UV radiation with these formulated solutions. The films were characterized to determine film hardness, gel and tensile properties. Jute yarns were treated with these formulated solutions and cured under the same UV source. More than 80% grafting occurred with the yarn; mechanical strength of the treated yarn increased to 55% and its elongation enhanced by 3 fold. Simulating weathering caused tensile strength loss between 40 and 70% and elongation by 40-70% depending on the formulations. The jute yarn plastic composite was found to be quite durable in normal conditions but it can be made degradable in certain environmental conditions to different degrees depending on the nature of the formulations.

Uddin, M. Khabir; Khan, Mubarak A.; Ali, K. M. Idriss

1996-10-01

201

Poly(glycidyl methacrylate) grafted CdSe quantum dots by surface-initiated atom transfer radical polymerization: Novel synthesis, characterization, properties, and cytotoxicity studies  

NASA Astrophysics Data System (ADS)

A novel approach for the synthesis of poly(glycidyl methacrylate) grafted CdSe quantum dot (QDs) (PGMA-g-CdSe) was developed. The PGMA-g-CdSe nanohybrids were synthesized by the surface-initiated atom transfer radical polymerization of glycidyl methacrylate from the surface of the strategic initiator, CdSe-BrIB QDs prepared by the interaction of 2-bromoisobutyryl bromide (BrIB) and CdSe-OH QDs. The structure, morphology, and optical property of the PGMA-g-CdSe nanohybrids were analyzed by FT-IR, XPS, TGA, XRD, TEM, and PL. The as-synthesized PGMA-g-CdSe nanohybrids having multi-epoxide groups were employed for the direct coupling of biotin via ring-opening reaction of the epoxide groups to afford the Biotin-f-PGMA-g-CdSe nanobioconjugate. The covalent immobilization of biotin onto PGMA-g-CdSe was confirmed by FT-IR, XPS, and EDX. Biocompatibility and imaging properties of the Biotin-f-PGMA-g-CdSe were investigated by MTT bioassay and PL analysis, respectively. The cell viability study suggested that the biocompatibility was significantly enhanced by the functionalization of CdSe QDs by biotin and PGMA.

Bach, Long Giang; Islam, Md. Rafiqul; Lee, Doh Chang; Lim, Kwon Taek

2013-10-01

202

Surface-Functionalized and Surface-Functionalizable Poly(vinylidene fluoride) Graft Copolymer Membranes via Click Chemistry and Atom Transfer Radical Polymerization.  

PubMed

Poly(vinylidene fluoride) (PVDF) with azide-functionalized poly(glycidyl methacrylate) (PGMA) side chains (PVDF-g-P[GMA-(N(3))(OH)]) were synthesized via free radical-initiated graft copolymerization of glycidyl methacrylate (GMA) from ozone-pretreated PVDF backbone (PVDF-g-PGMA), followed by reaction of the oxirane rings in the GMA side chains with sodium azide. Alkyne-functionalized poly(N-isopropylacrylamide) (alkynyl-PNIPAM), prepared a priori by atom transfer radical polymerization (ATRP), was used for the click reaction with the azido-containing PGMA side chains of the PVDF-g-P[GMA-(N(3))(OH)] copolymer to give rise to the thermoresponsive PVDF-g-P[GMA-click-PNIPAM] copolymer. Both the PVDF-g-P[GMA-(N(3))(OH)] and PVDF-g-P[GMA-click-PNIPAM] copolymers can be readily cast into microporous membranes by phase inversion in an aqueous medium. The PVDF-g-P[GMA-(N(3))(OH)] microporous membranes with azido-containing surfaces could be further functionalized via surface click reaction with alkyne-terminated PNIPAM of controlled chain lengths to obtain the PVDF-g-P[GMA-click-PNIPAM](surface) microporous membranes. The surface composition and morphology of the PVDF-g-P[GMA-click-PNIPAM] membranes can be adjusted by the temperature of casting medium, while the flux through both types of membranes exhibits thermoresponsive behavior. PMID:21341769

Cai, Tao; Neoh, K G; Kang, E T; Teo, S L M

2011-02-22

203

Separation of transition metals on a poly-iminodiacetic acid grafted polymeric resin column with post-column reaction detection utilising a paired emitter-detector diode system.  

PubMed

The selectivity, retention and separation of transition metals on a short (2 mm x 50 mm) column packed with a poly-iminodiacetic acid functionalised polymer 10 microm resin (Dionex ProPac IMAC-10) are presented. This stationary phase, typically used for the separation of proteins, is composed of long chain poly-iminodiacetic acid groups grafted to a hydrophilic layer surrounding a 10 microm polymeric bead. Through the use of a combination of a multi-step pH and picolinic acid gradient, the separation of magnesium, iron, cobalt, cadmium, zinc, lead and copper was possible, followed by post-column reaction with 4-(2-pyridylazo) resorcinol (PAR) and absorbance detection at 510 nm using a novel and inexpensive optical detector, comprised of two light emitting diodes with one acting as a light source and the other as a detector. Column efficiency for selective transition metals was in excess of N=10,000, with the baseline separation of seven metal cations in <3 min possible under optimised conditions. Detection limits of between 5 and 81 microg/L were possible based upon a 50 microL injection volume. PMID:18778827

Barron, Leon; O'Toole, Martina; Diamond, Dermot; Nesterenko, Pavel N; Paull, Brett

2008-08-19

204

Approach to cross-linked polynorbornene/ZnO nanocomposites through nitroxide-mediated free radical graft polymerization and in situ hydrolysis  

NASA Astrophysics Data System (ADS)

In this study, we reported an alternative strategy for fabricating stable cross-linked poly(butoxymethylenenorbornene-co-norbornene-2-carboxaldehyde)/ZnO (P(BN/NCA)/ZnO) nanocomposite films based on nitroxide-mediated free radical polymerization (NMRP) and in situ hydrolysis. Firstly, the macroinitiator poly(butoxymethylenenorbornene-co-norbornene-2-carboxaldehyde) alkoxyamine (P(BN/NCA)-TIPNO) was synthesized through the attachment of an alkoxyamine to polynorbornene derivative. And then the cross-linked graft copolymers poly(butoxymethylenenorbornene-co-norbornene-2-carboxaldehyde)-g-poly(zinc dimethacrylate) (P(BN/NCA)-g-PZDMA) were prepared using zinc dimethacrylate (ZDMA) and the as-prepared macroinitiator P(BN/NCA)-TIPNO by NMRP. Due to the two CC bonds in each ZDMA molecule, the resulting cross-linked polymer connected the precursor of ZnO nanocrystals and polymer with covalent band, leading to a homogenous distribution of Zn2+ at the molecular level. Finally, ZnO nanocrystals were generated in situ by hydrolyzing the polymer film in NaOH aqueous solution. ZnO nanocrystals were homogeneously dispersed in the cross-linked polymer matrix without aggregation. Compared with the physical blending of non-cross-linked P(BN/NCA)/ZnO nanocomposite film, the cross-linked P(BN/NCA)/ZnO nanocomposite films exhibited good optical properties and photoluminescence (PL) stability owing to the function of cross-linked template.

Li, Fan; Zhang, Lin; Chen, Yiwang

2012-07-01

205

Development of Functional Adsorbent From Textile Cotton Waste by Radiation Induced Grafting Process: Equilibrium and Kinetic Studies of Acid Dye Adsorption  

Microsoft Academic Search

An environment benign-aqueous solvent based-single step-radiation induced grafting process was used to graft Poly(vinylbenzyltrimethyl ammonium)chloride (PVBT) onto cellulosic cotton textile waste to transform it in to a valuable cationic adsorbent (PVBT-g-Cellulose). The PVBT-g-Cellulose adsorbent was characterized by grafting yield determination, elemental analysis, Scanning electron microscope (SEM) and Fourier transformed infrared (FTIR) spectroscopy. The PVBT-g-Cellulose adsorbent, investigated for removal of model

Virendra Kumar; N. K. Goel; Y. K. Bhardwaj; S. Sabharwal; Lalit Varshney

2012-01-01

206

Polymer degradation during radiation-induced emulsion polymerization of styrene. [. gamma. rays  

Microsoft Academic Search

Styrene was polymerized in emulsion with initiation by ..gamma..-rays at a dose rate of 0.6 Mrad\\/hr. Polymerization rates were as expected from previous reports by others. No branching or crosslinking was detectable, and the anti M\\/sub w\\/\\/anti M\\/sub n\\/ ratio of the polystyrene did not change significantly during the course of the polymerization reaction. The molecular weight of the product

K. Sato; A. Rudin; R. Y. M. Huang

1976-01-01

207

Molecularly imprinted polymer membranes for substance-selective solid-phase extraction from water by surface photo-grafting polymerization.  

PubMed

Hydrophilized polyvinylidene fluoride microfiltration membranes were surface-modified in the presence of a template (terbumeton) in methanol with a graft copolymer of a functional monomer (2-acrylamido-2-methyl-1-propane sulfonic acid, AMPS, methacrylic acid, MAA, or acrylic acid, AA) and a cross-linker (N,N'-methylene-bis-acrylamide) using UV irradiation and benzophenone as photoinitiator. As result, membranes covered with a thin layer of imprinted polymer selective to terbumeton were obtained. Blank membranes were prepared with the same monomer composition, but in the absence of the template. The membranes' capacity to adsorb terbumetone from aqueous solution was evaluated yielding information regarding the effect of polymer synthesis (type and concentration of functional monomer, concentration of cross-linker) on the resulting membranes' recognition properties. UV spectroscopic studies of the interactions with terbumetone revealed that AMPS forms a stronger complex than MAA and AA. In agreement with that finding, imprinting with AMPS gave higher affinities than with MAA and AA. The terbumeton-imprinted membranes showed significantly higher sorption capability to this herbicide than to similar compounds (atrazine, desmetryn, metribuzine). With the novel surface modification technology, the low non-specific binding properties of the hydrophilized microfiltration membrane could successfully be combined with the receptor properties of molecular imprints, yielding substance-specific molecularly imprinted polymer composite membranes. The high affinity of these synthetic affinity membranes to triazine herbicides together with their straightforward and inexpensive preparation provides a good basis for the development of applications of imprinted polymers in separation processes such as solid-phase extraction. PMID:11217051

Sergeyev, T A; Matuschewski, H; Piletsky, S A; Bendig, J; Schedler, U; Ulbricht, M

2001-01-12

208

Magnetic molecularly imprinted nanoparticles based on grafting polymerization for selective detection of 4-nitrophenol in aqueous samples.  

PubMed

In this study, an analytical procedure for the selective extraction and detection of 4-nitrophenol (4-NP) was investigated by using of molecularly imprinted polymer on the surface of magnetic nanoparticles (MNPs). The magnetic nanoparticles were modified by tetraethyl orthosilicate (TEOS) and 3-methacryloxypropyl trimethoxysilane (MPTS) before imprinting. The magnetic molecularly imprinted polymer (MMIP) was polymerized at the surface of modified MNPs by using of methacrylic acid (MAA) as functional monomer, 4-NP as template and ethylene glycol dimethacrylate (EGDMA) as cross-linker. Experimental design by the Taguchi method was used for the optimization of synthesis procedure of imprinted polymer. The resulting MMIP showed high adsorption capacity, proper selectivity and fast kinetic binding for the template molecule. It was characterized by Fourier transform infrared (FT-IR) analysis, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods. The maximum adsorption capacity of MMIP was obtained as 57.8mgg(-1) and it took about 2h to achieve the equilibrium state. The adsorption curve of MMIP was also fitted with the Freundlich isotherm equation. The assay exhibited a linear range of 25-1000?gL(-1) for 4-NP with the correlation coefficient (R(2)) of 0.995. The method was also examined for the analysis of 4-NPs in seawater. For recovery evaluation, the seawater samples were spiked at two concentration levels of 50 and 100?gL(-1) of 4-NPs and the recovery values were in the range of 79.3-99.8%. The relative standard deviations (RSD) for the recoveries were less than 5.2%. PMID:23465129

Mehdinia, Ali; Baradaran Kayyal, Tohid; Jabbari, Ali; Aziz-Zanjani, Mohammad Ovais; Ziaei, Ehsan

2013-01-29

209

Generation of the second harmonic of laser radiation in noncentrosymmetrical polymeric systems  

Microsoft Academic Search

Second-order nonlinear optical properties in polymeric media and the mechanisms of generation and relaxation of the second harmonic of a polarised laser beam are discussed. The relationships between the chemical structures of the polymeric systems and the transport characteristics of the charge carriers are considered and the influence of the captured charges on the parameters of the second harmonic relaxation

Anatolii V Vannikov; Antonina D Grishina; R W Rychwalski; Anatolii T Ponomarenko

1998-01-01

210

Microfiltration membranes prepared from polyethersulfone powder grafted with acrylic acid by simultaneous irradiation and their pH dependence  

NASA Astrophysics Data System (ADS)

Polyethersulfone (PES) powder was grafted with acrylic acid (AAc) by simultaneous ?-ray irradiation. The kinetics of the radiation induced graft polymerization was studied and the grafted PES powder was characterized. Then, microfiltration (MF) membranes were prepared from PES-g-PAAc powder with different degrees of grafting (DG) under phase inversion method. The swelling behavior and the mean pore size of MF membranes were measured, and the filtration property was tested. The results showed that the pore size and the flux of MF membranes increased with the increase in DG. And, MF membranes’ properties were dependent on the pH value.

Deng, Bo; Li, Jingye; Hou, Zhengchi; Yao, Side; Shi, Liuqing; Liang, Guoming; Sheng, Kanglong

2008-07-01

211

Polymer Dissolution Characteristics of Radiation-Induced Grafted Resist in X-Ray Lithography  

NASA Astrophysics Data System (ADS)

Dissolution characteristics of grafted resist by X-ray irradiation are investigated. Poly(phenyl methacrylate) (PPhMA) which is used as a base resist is grafted by acrylic acid after X-ray exposure. The developed resist pattern was found to be significantly tapered with an increase in development time. Such a deterioration is attributed to swelling of the resist polymer and dissolution of less fully grafted components by developer. The swelling and dissolution of grafted resist during development is drastically minimized by the formation of a cross-linked structure in the grafted resist by thermal dehydration of acrylic acids. As a result, a grafted resist pattern with feature size as small as 0.3 ?m is successfully obtained at the high X-ray sensitivity of 50 mJ/cm2.

Oizumi, Hiroaki; Sohda, Yasunari; Mochiji, Kozo

1991-02-01

212

Radiation-Associated Fracture Nonunion of the Clavicle Treated with Locking Plate Fixation and Autologous Bone Grafting  

PubMed Central

We describe a case of radiation-associated fracture nonunion of the clavicle, which was treated by locking plate fixation and autologous bone grafting. The patient was a 67-year old man who received 70?Gy radiation therapy to treat nasopharyngeal carcinoma. Eight years later, he suffered a pathological fracture of the right clavicle. One year after the fracture, surgical treatment was performed due to persistent pain and weakness. Radiographs demonstrated atrophic nonunion. Bone scan demonstrated hot uptake at both ends of the fractured bone. MRI demonstrated a formation of pseudoarthrosis with fluid collection and suggested bone marrow edema at both ends of the fracture fragments. In surgery, fibrous pseudoarthrosis tissue was excised and both ends of the fracture fragments were refreshed to identify bleeding. Open reduction and internal fixation using a 7-hole locking plate and autologous bone grafting were performed. Successful bony union was obtained 1 year postoperatively, and no adverse events were observed up to 52 months after the operation. Our case suggests that a locking plate provides sufficient fixation and autologous bone grafting is effective in enhancing bone healing in a radiation-associated fracture nonunion of the clavicle in which it is difficult to achieve bony union.

Lee, Sang Yang; Nishida, Kotaro; Kuroda, Ryosuke; Kurosaka, Masahiro

2012-01-01

213

Radiation-induced grafting of N-isopropylacrylamide onto the brominated poly(2,6-dimethyl-1,4-phenylene oxide) membranes  

NASA Astrophysics Data System (ADS)

A novel thermo-sensitive switching membrane has been prepared by radiation-induced simultaneous grafting N-isopropylacrylamide (NIPAAm) onto brominated poly(2,6-dimethyl-1,4-phenylene oxide) BPPO. In order to attain a high grafting degree, the effects of dose, dose rate, concentration of NIPAAm, concentration of inhibitor Cu2+, membrane thickness and solvents were investigated. The grafting process was characterized by FTIR spectroscopy and the highest grafting degree obtained was 7.87%. The thermo-sensitive property of the grafted membrane was measured by water flux (20 48 °C). The results showed that the grafted membrane could respond instantly to environmental temperature changes, and there was a sharp change around the lower critical solution temperature as it is normally seen in PNIPAAm hydrogel.

Lin, Zhan; Xu, Tongwen; Zhang, Lei

2006-04-01

214

Generation of the second harmonic of laser radiation in noncentrosymmetrical polymeric systems  

NASA Astrophysics Data System (ADS)

Second-order nonlinear optical properties in polymeric media and the mechanisms of generation and relaxation of the second harmonic of a polarised laser beam are discussed. The relationships between the chemical structures of the polymeric systems and the transport characteristics of the charge carriers are considered and the influence of the captured charges on the parameters of the second harmonic relaxation are analysed. It is shown that the kinetics of second harmonic relaxation in the polymeric systems of the host-guest type is determined entirely by the decay kinetics of the surface potential. The bibliography includes 98 references.

Vannikov, Anatolii V.; Grishina, Antonina D.; Rychwalski, R. W.; Ponomarenko, Anatolii T.

1998-06-01

215

Gamma radiation induced polymerization of vinyl monomers in dense CO2  

NASA Astrophysics Data System (ADS)

The dispersion polymerization of methyl methacrylate in dense carbon dioxide, initiated by ?-rays, utilizing different polysiloxanes as polymeric stabilizers, was investigated. The progress of the reaction, as a function of the irradiation dose, was also studied and the occurrence of a gel effect has been detected. For comparison, the dispersion polymerization has been carried out in supercritical conditions (/T=65°C and 38MPa) in the presence of 2,2'-azobis(isobutyronitrile) (AIBN) as initiator. High molecular weight polymer (Mw>1000kg/mol) with narrow molecular weight distribution has been obtained both with ?-rays and AIBN. The electron scanning micrographs show that regular spherical particles (average diameter ca. 2.5?m) with narrow particle size distribution have been obtained through the dispersion polymerization mechanism in CO2.

Caputo, G.; Galia, A.; Scrò, F.; Spadaro, G.; Filardo, G.

2002-01-01

216

Effect of gamma radiation on the mechanical and barrier properties of HEMA grafted chitosan-based films  

NASA Astrophysics Data System (ADS)

Chitosan films were prepared by dissolving 1% (w/v) chitosan powder in 2% (w/v) aqueous acetic acid solution. Chitosan films were prepared by solution casting. The values of puncture strength (PS), viscoelasticity coefficient and water vapor permeability (WVP) of the films were found to be 565 N/mm, 35%, and 3.30 g mm/m2 day kPa, respectively. Chitosan solution was exposed to gamma irradiation (0.1-5 kGy) and it was revealed that PS values were reduced significantly (p?0.05) after 1 kGy dose and it was not possible to form films after 5 kGy. Monomer, 2-hydroxyethyl methacrylate (HEMA) solution (0.1-1%, w/v) was incorporated into the chitosan solution and the formulation was exposed to gamma irradiation (0.3 kGy). A 0.1% (w/v) HEMA concentration at 0.3 kGy dose was found optimal-based on PS values for chitosan grafting. Then radiation dose (0.1-5 kGy) was optimized for HEMA grafting. The highest PS values (672 N/mm) were found at 0.7 kGy. The WVP of the grafted films improved significantly (p?0.05) with the rise of radiation dose.

Khan, Avik; Huq, Tanzina; Khan, Ruhul A.; Dussault, Dominic; Salmieri, Stephane; Lacroix, Monique

2012-08-01

217

Cation exchange membranes by radiation-induced graft copolymerization of styrene onto PFA copolymer films. I. Preparation and characterization of the graft copolymer  

Microsoft Academic Search

PFA-g-polystyrene graft copolymers were prepared by simultaneous radi- ation-induced graft copolymerization of styrene onto poly(tetrafluoroethylene-co-per- fluorovinyl ether) (PFA) films. The effects of grafting conditions such as monomer concentration, dose, and dose rate were investigated. Three solvents, i.e., methanol, benzene, and dichloromethane, were used as diluents in this grafting system. Of the three solvents employed, dichloromethane was found to greatly enhance

Mohamed Mahmoud Nasef; Hamdani Saidi; Hussin Mohd Nor; Khairul Zaman M. Dahlan; Kamaruddin Hashim

1999-01-01

218

Role of radiolytically generated species in radiation induced polymerization of sodium p-styrene sulphonate (SSS) in aqueous solution: Steady state and pulse radiolysis study  

Microsoft Academic Search

Radiation induced polymerization of sodium p-styrene sulphonate (SSS) in aqueous solution has been investigated by steady state and pulse radiolysis techniques. Effect of dose, dose rate, monomer concentration, pH and ambient conditions on polymerization was investigated. The reactions of primary radicals of water radiolysis such as OH radical, e-aq, H atom, O- and some oxidizing radicals like N3, Cl-2,Br-2, and

Y. K. Bhardwaj; H. Mohan; S. Sabharwal; A. B. Majali

2000-01-01

219

Role of radiolytically generated species in radiation induced polymerization of sodium p-styrene sulphonate (SSS) in aqueous solution: Steady state and pulse radiolysis study  

Microsoft Academic Search

Radiation induced polymerization of sodium p-styrene sulphonate (SSS) in aqueous solution has been investigated by steady state and pulse radiolysis techniques. Effect of dose, dose rate, monomer concentration, pH and ambient conditions on polymerization was investigated. The reactions of primary radicals of water radiolysis such as OH radical, e?aq, H atom, O? and some oxidizing radicals like N3, Cl?2,Br?2, and

Y. K. Bhardwaj; H. Mohan; S. Sabharwal; A. B. Majali

2000-01-01

220

EPR investigation on radiation-induced graft copolymerization of styrene onto polyethylene: Energy transfer effects  

NASA Astrophysics Data System (ADS)

In this paper, energy transfer phenomena concerning the in-source graft copolymerization of styrene onto LDPE were investigated through the EPR analysis of the radical intermediates. The model solution experiments have shown a substantial deviation of the experimental G (radicals) values with respect to the additivity law, which reflect the negative effect of the styrene monomer concentration on the initiation rate of the graft copolymerization. The EPR measurements performed on polyethylene-co-styrene graft copolymers of various composition following low-temperature vacuum gamma irradiation have confirmed the decrease of the total radical yields with increasing the styrene concentration. The effect was partly attributed to the heterogeneity of the graft copolymer matrix and to the lack of molecular mobility in the solid state at low temperature, which prevents the attainment of the favourable geometrical configurations in intermolecular energy and charge transfer events.

Salih, M. A.; Buttafava, A.; Ravasio, U.; Mariani, M.; Faucitano, A.

2007-08-01

221

Preparation, characterization and in vitro release study of a glutathione-dependent polymeric prodrug Cis-3-(9H-purin-6-ylthio)-acrylic acid-graft-carboxymethyl chitosan.  

PubMed

In this work, an amphiphilic polymeric prodrug Cis-3-(9H-purin-6-ylthio)-acrylic acid-graft-carboxymethyl chitosan (PTA-g-CMCS) was designed and synthesized. In aqueous solution, this grafted polymer can self-assemble into spherical micelles with a size ranging from 104 to 285 nm and zeta potential ranging from -12.3 to -20.1 mV. For the release study, less than 24% of 6-Mercaptopurine (6-MP) was released from PTA-g-CMCS1 in the media containing 2 and 100 ?M glutathione (GSH), whereas 37%, 54% and 75% of 6-MP was released from the media with GSH of 1, 2 and 10mM, respectively. Besides, pH and drug content of the polymeric prodrug only presented slight influence on the 6-MP release. MTT assay demonstrated that this system had higher inhibition ratio on HL-60 cells (human promyelocytic leukemia cells) in the presence of GSH and lower cytotoxicity on mouse fibroblast cell line (L929). Therefore, this nano-sized system is glutathione-dependent, and it can be employed as a potential carrier for the controlled release of 6-MP. PMID:22750430

Gong, Xiao-Yu; Yin, Yi-Hua; Huang, Zhi-Jun; Lu, Bo; Xu, Pei-Hu; Zheng, Hua; Xiong, Fu-Liang; Xu, Hai-Xing; Xiong, Xiong; Gu, Xing-Bao

2012-06-26

222

Novel features of radiation-induced bystander signaling in Arabidopsis thaliana demonstrated using root micro-grafting  

PubMed Central

Radiation-induced bystander effects (RIBE) have been well demonstrated in whole organisms, as well as in single-cell culture models in vitro and multi-cellular tissues models in vitro, however, the underlying mechanisms remain unclear, including the temporal and spatial course of bystander signaling. The RIBE in vivo has been shown to exist in the model plant Arabidopsis thaliana (A. thaliana). Importantly, the unique plant grafting provides a delicate approach for studying the temporal and spatial course of bystander signaling in the context of whole plants. In our previous study, the time course of bystander signaling in plants has been well demonstrated using the root micro-grafting technique. In this study, we further investigated the temporal cooperation pattern of multiple bystander signals, the directionality of bystander signaling, and the effect of bystander tissues on the bystander signaling. The results showed that the bystander response could also be induced efficiently when the asynchronously generated bystander signals reached the bystander tissues in the same period, but not when they entered into the bystander tissues in an inversed sequence. The absence of bystander response in root-inversed grafting indicated that the bystander signaling along roots might be of directionality. The bystander signaling was shown to be independent of the bystander tissues.

Wang, Ting; Li, Fanghua; Xu, Wei; Bian, Po; Wu, Yuejin; Wu, Lijun

2012-01-01

223

Adsorption of Cr(VI) using cellulose microsphere-based adsorbent prepared by radiation-induced grafting  

NASA Astrophysics Data System (ADS)

Cellulose microsphere (CMS) adsorbent was prepared by radiation-induced grafting of dimethylaminoethyl methacrylate (DMAEMA) onto CMS followed by a protonation process. The FTIR spectra analysis proved that PDMAEMA was grafted successfully onto CMS. The adsorption of Cr(VI) onto the resulting adsorbent was very fast, the equilibrium adsorption could be achieved within 15 min. The adsorption capacity strongly depended on the pH of the solution, which was attributed to the change of both the existed forms of Cr(VI) and the tertiary-ammonium group of PDMAEMA grafted CMS with the pH. A maximum Cr(VI) uptake (ca. 78 mg g-1) was obtained as the pH was in the range of 3.0-6.0. However, even in strong acid media (pH 1.3), the adsorbents still showed a Cr(VI) uptake of 30 mg g-1. The adsorption behavior of the resultant absorbent could be described with the Langmuir mode. This adsorbent has potential application for removing heavy metal ion pollutants (e.g. Cr(VI)) from wastewater.

Li, Cancan; Zhang, Youwei; Peng, Jing; Wu, Hao; Li, Jiuqiang; Zhai, Maolin

2012-08-01

224

UV radiation-induced surface modulation time evolution in polymeric materials  

NASA Astrophysics Data System (ADS)

The reorganization processes at submicron level of the polymeric materials have been investigated because of their applications in optoelectronics and bio-science. We have obtained surface relief modulation in single step processing on the photo resist and polysiloxane films. But for technical applications the time evolution and stability of the induced surface structure is an important parameter and is a problem to be discussed. In case of single step surface relief formation on polymeric materials the process is connected with the photochromic behavior of the materials. As it is known the UV light induced effects on the material structure are reversible under the action of visible light, but with different speeds. In this report is analyzed the time evolution of the surface modulation obtained under the action of the UV light for azopolymers with different structures.

Apostol, I.; Apostol, D.; Damian, V.; Iordache, I.; Hurduc, N.; Sava, I.; Sacarescu, L.; Stoica, I.

2009-05-01

225

Synthesis and characterization of uniform polyepoxide micrometer sized particles by redox graft polymerization of glycidyl methacylate on oxidized polystyrene and polydivinylbenzene microspheres for enzyme immobilization  

Microsoft Academic Search

Polystyrene template microspheres of narrow size distribution were prepared by dispersion polymerization of styrene in 2-methoxyethanol. Uniform polystyrene\\/poly(divinyl benzene) composite microspheres were formed by a single-step swelling process of the polystyrene template microspheres with dibutyl phthalate droplets containing divinyl benzene and benzoyl peroxide, followed by polymerization at 73 °C. Uniform poly(divinyl benzene) microspheres of higher surface area were produced by dissolution

Melany Omer-Mizrahi; Shlomo Margel

2010-01-01

226

Surface modification of polyethylene by radiation-induced grafting for adhesive bonding. IV. Improvement in wet peel strength. [Gamma radiation  

Microsoft Academic Search

Adhesive joints of hydrolyzed methyl acrylate grafts, bonded with epoxy adhesives, yield extremely high peel strength (adherend failure) in dry conditions. However, when the joints are exposed to humid environments, the peel strength rapidly decreases with exposure time and then reaches a constant value (wet peel strength). Since the locus of failure changes from the adherend to the homopolymer layer

S. Yamakawa; F. Yamamoto

1980-01-01

227

Utilization of recycled polypropylene-acrylate grafted nonwoven for the removal of oil from water.  

PubMed

To solve water pollution caused by oil spillage, a new sorbent was prepared by radiation-induced graft polymerization. Acrylate monomer was introduced to polypropylene nonwoven and hydrophobic groups were introduced by the grafting method. The grafting degree of sorbent was determined as a function of monomer concentration and solvent solubility for monomer. Fourier transform-infrared spectra and static contact angle measurements were used to characterize the chemical changes of the polypropylene nonwoven surface. The grafted sorbent showed a fast sorption rate and a maximum sorption capacity of 13.56 g/g for diesel oil, while the original polypropylene nonwoven was only 7.48 g/g. In addition, retention measurement and the reusability test were conducted to evaluate the suitability of the polypropylene-acrylate grafted nonwoven for the treatment of oil spillage. PMID:23012771

Li, Shaoning; Wei, Junfu; Wang, Lei; Wang, Ao; Yang, Hang; Nie, Yuexia

2012-09-01

228

New trends of radiation processing applications  

NASA Astrophysics Data System (ADS)

Major fields of radiation processing applications are: polymeric materials, food processing, sterilization of medical products and environmental conservation. There are about 200 60Co gamma irradiation facilities and 700 electron beam accelerators, mainly for commercial purposes, throughout the world. Radiation cross-linking and grafting techniques of polymeric materials have been providing many unique products including heat materials, heat shrinkable materials, curing of coatings and battery separators. Extensive studies have been devoted to the development of bio-medical materials using radiation processing to prepare bio-compatible materials and controlled release of drugs. New wound dressings have been successfully developed in Poland and Israel for commercial clinical use.

Machi, Sueo

1996-03-01

229

Anionic grafts of monomers onto coal substrates  

SciTech Connect

Anionic grafting of olefinic monomers onto coal substrates is disclosed. The process comprises grafting polymeric side chains onto coal by contacting coal with a covalently bonded alkyl or aryl alkali metal initiator to generate carbon-alkali metal bonds and then reacting these bonds with an olefinically unsaturated monomer for a time sufficient to produce a grafted coal product having polymeric side chains bonded to the coal. The resulting coal grafts evidence enhanced solubility in organic solvents, and liquids derived from the coal grafts evidence reduced sulfur content.

Ebert, L.B.; Matty, L.J.

1981-04-21

230

Gamma-ray co-irradiation induced graft polymerization of NVP and SSS onto polypropylene non-woven fabric and its blood compatibility  

NASA Astrophysics Data System (ADS)

Sodium styrenesulfonate was grafted onto PPNWF via ?-ray co-irradiation method with the existence of N-vinyl-2-pyrrolidone. The effect of absorbed dose, dose rate and concentration of binary monomer on the degree of grafting was investigated. The surface chemical change was characterized by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The wettability was characterized through the measurement of adsorption percentage of water and phosphate buffer solution (PBS). The result demonstrated that the grafted poly(NVP-co-SSS) chains can improve the hydrophilicity of PPNWF. Furthermore, the modified PPNWF has good blood compatibility, such as low hemolysis rate, low platelet adhesion and effectively extending the blood coagulation times. Consequently, hydrophilicity and hemocompatibility of PPNWF were greatly enhanced by the immobilization of poly(NVP-co-SSS) chains.

Li, Rong; Wang, Hengdong; Wang, Wenfeng; Ye, Yin

2013-10-01

231

Surface Morphology of Radiation-Grafted Binary Copolymers Measured in Buffer Solution under Swelling Condition  

NASA Astrophysics Data System (ADS)

pH-dependent binary graft copolymers, [polypropylene (PP)-g-2-(dimethylamino)ethylmethacrylate (DMAEMA)-g-N-isopropylacrylamide (NIPAAm) and (PP-g-4-vinylpyridine (4VP))-g-NIPAAm], synthesized by a two-step gamma-irradiation method, were characterized in terms of surface morphology under swelling condition. A confocal laser microscope with a water-immersion objective lens was employed for noncontact surface profile measurement of an extremely soft surface. Surface morphology was significantly different between these two binary copolymers, suggesting that the surface morphology of the binary copolymer reflected that of the first graft layer. Surface roughness was also analyzed as a function of the pH of the swelling buffer solution. Surface roughness increased with swelling ratio, and it further increased at lower pH, consistent with the results of a swelling ratio experiment previously reported.

Meléndez-Ortiz, Hector Ivan; Bucio, Emilio; Isoshima, Takashi; Ito, Hiromi; Hara, Masahiko

2010-01-01

232

Radiation-induced graft polymerization is the key to develop high-performance functional materials for protein purification  

NASA Astrophysics Data System (ADS)

We have described a preparation scheme for immobilizing polymer chains at a uniformly high density onto a microfiltration membrane. Highly efficient protein recovery was demonstrated by the results of the determination of breakthrough and elution curves. The three requirements of high rate, high capacity, and repeated use for the protein recovery were satisfied by ensuring the occurrence of convection, multilayer binding, and hydrophilization, respectively. In addition, easy scale-up to fabrication of a membrane module was verified on a small scale.

Saito, K.; Tsuneda, S.; Kim, M.; Kubota, N.; Sugita, K.; Sugo, T.

1999-05-01

233

Effect of monomer structure on radiation grafting of charge transfer complexes to synthetic and naturally occurring polymers  

NASA Astrophysics Data System (ADS)

Effect of monomer structure in photografting charge transfer (CT) complexes to typical substrates like wool, cellulose and polypropylene is reported. The importance of photoinitiators in these processes is examined. Maleic anhydride (MA) with triethylene glycol divinyl ether (DVE-3) is used as reference CT complex in this work. The additional monomers studied include the esters of MA as acceptors and vinyl acetate as donor. The role of solvent in these reactions is discussed, particularly the effect of aromatics in photografting to naturally occurring trunk polymers like wool and cellulose. The effect of the double bond molar ratio of the DA components in grafting is examined. The ultraviolet (UV) conditions for gel formation during photografting, hence the importance of homopolymer yields in these processes is reported. A plausible mechanism to explain the results from this photografting work is proposed. The significance of these photografting studies in the related field of curing, especially in UV and ionising radiation systems, is discussed.

Ng, L.-T.; Garnett, J. L.; Zilic, E.; Nguyen, D.

2001-07-01

234

Ozone-induced grafting phosphorylcholine polymer onto silicone film grafting 2-methacryloyloxyethyl phosphorylcholine onto silicone film to improve hemocompatibility  

Microsoft Academic Search

Ozonization, a novel surface modification method, has been developed to improve hemocompatibility of polymeric biomaterials. The silicone film was exposed to ozone and then followed by grafted polymerization with 2-methacryloyloxyethyl phosphorylcholine (MPC). The surface graft polymerization was confirmed by X-ray photon spectroscopy and ATR-FTIR. Surface hydrophilicity was investigated by measuring the contact angles and MPC polymer grafted silicone film show

Jianmin Xu; Youling Yuan; Bing Shan; Jian Shen; Sicong Lin

2003-01-01

235

Preparation of hydrophilic monodisperse microspheres by radiation precipitation polymerization and its characteristics  

Microsoft Academic Search

A new preparation method for monodisperse polymer microspheres with a hydrophilic property has been investigated by utilizing an irradiation method. Hydrophilic microspheres were synthesized by radiation precipitation copolymerization using polyethylenglycol dimethacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, and methacrylic acid monomer. The diameter of the microspheres prepared was 0.3–1 ?m, in which the irradiation was carried out without catalyzer at room temperature

M. Kumakura

1995-01-01

236

Radiation-induced polymerization of ?(+)-pinene and synthesis of optically active ?(+)/?(-)pinene polymers and copolymers  

NASA Astrophysics Data System (ADS)

Poly-?(+)-pinene (pB(+)p) was synthesized with ? irradiation of the monomer ?(+)-pinene in bulk under vacuum at 1181 kGy. Also scalemic mixtures of ?(+)-pinene and ?(-)-pinene were irradiated at 1181 kGy to obtain synthetic copolymers of pB(+)/B(-)p. For comparison also ?(-)-pinene was converted into poly-?(-)-pinene (pB(-)p) under the identical conditions adopted for its enantiomer. Furthermore pB(+)p and pB(-)p were also synthesized by thermal processing under the action of a chemical free radical initiator. The optical rotatory dispersion (ORD) of all pBp resins synthesized were accurately studied in the spectral range comprised between 375 and 625 nm and a curious asymmetry in the ORD of pB(+)p versus the ORD of pB(-)p is reported. Furthermore, it is shown that (+)-p-menth-1-ene and (-)-p-menth-1-ene are useful as a model compounds for the pBp resins and for the explanation of the amplification of the optical activity of the ?(+)-pinene and ?(-)-pinene after their ring-opening polymerization to pB(+)p and pB(-)p. The pBp resins were studied also by FT-IR spectroscopy and by thermal analysis (TGA and DTG).

Cataldo, Franco; Lilla, Edo; Ursini, Ornella

2011-06-01

237

An efficient approach to obtaining water-compatible and stimuli-responsive molecularly imprinted polymers by the facile surface-grafting of functional polymer brushes via RAFT polymerization  

Microsoft Academic Search

A new and efficient approach to obtaining molecularly imprinted polymers (MIPs) with both pure water-compatible (i.e., applicable in the pure aqueous environments) and stimuli-responsive binding properties is described, whose proof-of-principle is demonstrated by the facile modification of the preformed MIP microspheres via surface-initiated reversible addition–fragmentation chain transfer (RAFT) polymerization of N-isopropylacrylamide (NIPAAm). The presence of poly(NIPAAm) (PNIPAAm) brushes on the

Guoqing Pan; Ying Zhang; Xianzhi Guo; Chenxi Li; Huiqi Zhang

2010-01-01

238

Uranium Sorption by Pseudomonas Biomass Immobilized in Radiation Polymerized Polyacrylamide Bio-Beads  

Microsoft Academic Search

A Pseudomonas strain identified as a potent biosorbent of uranium (U) and thorium was immobilized in radiation-induced polyacrylamide matrix for its application in radionuclide containing wastewater treatment. The immobilized biomass exhibited a high U sorption of 202 mg g dry wt. with its optimum at pH 5.0. A good fit of experimental data to the Freundlich model suggested multilayered uranium

S. F. DSOUZA; PINAKI SAR; SUFIA K. KAZY; B. S. KUBAL

2006-01-01

239

Controlled Release of Biomolecules from pH-Sensitive Hydrogels Prepared by Radiation Polymerization  

Microsoft Academic Search

Copolymers of 2-hydroxyethyl methacrylate and methacrylic acid based hydrogels were studied as hydrogel drug delivery systems. Radiation copolymerization of 2-hydroxyethyl methacrylate and methacrylic acid (mixed with 3,3'-azobis(6-hydroxy benzoic acid)(ABHB) as an azo derivative of 5-aminosalicylic acid were carried out with various amounts of methacryloyloxyethyl esters of terephthalic acid for crosslinking. The polymer structures were characterized by FTIR, 1H NMR, 13C

Mehrdad Mahkam

2004-01-01

240

Influence of radiation protocols on graft-vs-host disease incidence after bone-marrow transplantation in experimental models.  

PubMed

Bone-marrow transplantation is an approved curative treatment for many hemato- and oncologic diseases. Nevertheless, the severe acute clinical course of graft-vs-host disease (GVHD) after allogeneic bone-marrow transplantation is frequently fatal, and is to date not curable. Acute GVHD must, therefore, be prevented from the start of the bone-marrow transplantation by immunosuppressive medication, causing sometimes serious side effects. Therefore, new preventive strategies are tested, starting with animal experiments. Often mice are chosen for this kind of trial, and the clinical protocol of bone-marrow transplantation is transferred into the experimental settings. The first step to induce an acute GVHD is whole-body irradiation of the recipients. Several methods are available for this purpose: the most common is a 60cobalt source (gamma-irradiation); less common are a 137cesium source (gamma-irradiation) and a linear (particle) accelerator (photons). Differences between these radiation techniques can occur and can unexpectedly interfere with the results of the experiments. In this chapter, the materials and methods for bone-marrow transplantation in mice, with particular emphasis on the different radiation techniques, are explained; furthermore, the advantages and disadvantages in regard to the underlying physical principles will be discussed. PMID:15585937

Schwarte, Sebastian; Hoffmann, Matthias W

2005-01-01

241

The effect of nanocomposite polymeric layer on the radiation of antisymmetric zero-order Lamb wave in a piezoelectric plate contacting with liquid  

NASA Astrophysics Data System (ADS)

A nanocomposite polymeric layer is proposed to be used for increasing the efficiency of ultrasound radiation into the liquid by antisymmetric zero-order (A0) Lamb waves propagating in piezoelectric plates. The theoretical and experimental investigations of the influence of the nanocomposite polymeric layers on the efficiency and radiation angle of acoustic wave into liquid were carried out. It has been theoretically shown that the use of the layer of the polyethylene of low density with nanoparticles of cadmium sulfide of concentration 25% between the plate of 128YX LiNbO3 and water medium allows to increase the radiation attenuation on ~1 dB/? if the ratio of the thicknesses of the layer and plate is equal to 0.16 at the frequency of 1.3 MHz. The experimental data were in a good agreement with theoretical results. It has been also shown that the presence of nanocomposite film leads to the increase of the radiation angle of bulk acoustic wave in liquid and allows the effective operation of the radiator not only in the sweet water but also in salt one. The obtained results may be used for the development of effective radiators/receivers of acoustic waves in liquids for flow meters and for underwater communication systems.

Kuznetsova, I. E.; Zaitsev, B. D.; Borodina, I. A.; Shikhabudinov, A. M.; Teplykh, A. A.; Manga, E.; Feuillard, G.

2013-06-01

242

Fixation of three-dimensional states of deformation in polymers by ionizing radiation. Search for new polymeric materials.  

NASA Astrophysics Data System (ADS)

The fixation of three-dimensional states of deformation in polymers allows the analysis of ``special states'' of elastic stresses even in the interior of complex constructional units and machine parts. This is the reason for the fact that in spite of the development of modern experimental methods of the analysis of deformation, which are in general restricted to the deformation of the surface of the bodies, the classical ``photoelasticity'' is still an adequate procedure for solving technical problems. However there are several restrictions on the applicability of the presently used procedures. A potential way to overcome these restrictions is the use of ionizing radiation, which in several polymeric materials causes a more or less perfect fixation of three-dimensional states of deformation. The search for suitable polymers includes the modification of well-known materials like epoxy resins as well as the application and development of materials not yet used in this field of engineering. Preliminary results of the search for such new materials are presented. In selected polymers the stress-optical constant f? (S) typically increases with dose, whereas the optical creep behaves ambiguous on irradiation.

Schaudy, R.; Wendrinsky, J.; Beer, R. J.; Eberhardsteiner, J.

1995-02-01

243

Controlled release of biomolecules from pH-sensitive network polymers prepared by radiation polymerization.  

PubMed

Copolymers of 2-hydroxyethyl methacrylate (HEMA) and methacrylic acid (MAA) based hydrogels containing 5 and 10% of a cross-linking agent were studied as drug delivery systems. Terephthalic acid was covalently linked with HEMA, abbreviated as CA. Radiation copolymerization of HEMA and MAA, mixed with a particulate glibenclamide with the various ratios CA as crosslinking agent were carried out at the room temperature. The structure of the CA was confirmed by FTIR, H NMR and C NMR spectroscopy. The compositions of the cross-linked three-dimensional polymers were determined by FTIR spectroscopy. Glass transition temperature (T) of the network polymers was determined calorimetrically. The hydrolysis of drug-polymer conjugates was carried out in cellophane membrane dialysis bags containing an aqueous buffer solution (pH 7.4 and pH 1) at 37 degree C. The drug-release profiles indicate that amount drug release depends on their degree of swelling and cross-linking. PMID:15203894

Mahkam, Mehrdad; Allahverdipoor, Mojgan

2004-04-01

244

Radiation-grafted proton exchange membranes based on co-grafting from binary monomer mixtures into poly(ethylene-co-tetrafluoroethylene) (ETFE) film  

NASA Astrophysics Data System (ADS)

In this study, proton exchange membranes (PEMs) based on a poly(ethylene-co-tetrafluoroethylene) (ETFE) film were synthesized through the graft copolymerization of styrene and VTMS (vinyltrimethoxysilane), or styrene and TMSPM (3-(trimethoxysilyl) propyl methacrylate) binary monomer systems using a simultaneous irradiation method. The prepared membranes with the similar degrees of grafting were investigated by measuring ion exchange capacity, proton conductivity, water uptake, chemical stability, and dimensional stability. The results indicate that the silane-crosslinked proton exchange membrane (PEM) has not only lower water uptake and dimensional change but also high proton conductivity at low humidity condition compared to non-crosslinked poly(ethylene-co-tetrafluoroethylene)-g-poly(styrene sulfonic acid) (ETFE-g-PSSA). Also, the chemical stability of silane-crosslinked fuel cell membranes was more improved than that of non-crosslinked fuel cell membrane.

Sohn, Joon-Yong; Sung, Hae-Jun; Song, Joo-Myung; Shin, Junhwa; Nho, Young-Chang

2012-08-01

245

Radiation-induced grafting of styrene onto ultra-high molecular weight polyethylene powder for polymer electrolyte fuel cell application  

Microsoft Academic Search

Post-sulfonation of selective styrene-grafted ultra-high molecular weight polyethylene (UHMWPE-g-PS) films was carried out by chlorosulfonic acid and the properties of the membranes were investigated. The UHMWPE-g-PS films were previously prepared by initial ?-irradiation of polyethylene powder, grafting with styrene, followed by hot-pressing to process into films. The range of ion exchange capacities (IECs) obtained with different degrees of grafting (DG)

Tauqir A. Sherazi; Shujaat Ahmad; M. Akram Kashmiri; Dae Sik Kim; Michael D. Guiver

2009-01-01

246

Novel temperature-sensitive crosslinked polymeric nanocapsules  

Microsoft Academic Search

Novel temperature-sensitive polymeric nanocapsules crosslinked via amide groups were prepared by the surface-initiated atom transfer radical polymerization (SI-ATRP) technique based on the widely used sacrificial SiO2 nanoparticle templates. In the strategy developed, the silica templates were removed by being etched with HF to obtain the crosslinked polymeric nanocapsules after the poly(methyl acrylate) (PMA) chains grafted on the SiO2 templates were

Bin Mu; Peng Liu

2010-01-01

247

Organic\\/inorganic hybrid composites prepared by polymerization compounding and controlled free radical polymerization  

Microsoft Academic Search

A new method to produce highly filled and well dispersed polymer solid composites using controlled free radical polymerization has been developed. Grafting of polymers onto ultrafine silica was done in bulk polymerization at 120°C in presence of N-tert-butyl-1-diethylphosphono2,2-dimethyl propyl nitroxide (DEPN) as a nitroxide stable free radical. Optimum conditions for tert-butyl hydroperoxide grafting onto fumed silica were first determined. The

A Kasseh; A Ait-Kadi; B Riedl; J. F Pierson

2003-01-01

248

Prevention of graft rejection in allogeneic bone marrow transplantation. II. Preclinical studies with three radiation protocols  

SciTech Connect

Three radiotherapeutic regimens were compared in vitro to determine their immunosuppressive potential against non-MHC-restricted cytotoxic cells. Assays of natural killer and lymphokine-activated killer function, and cytotoxicity against allogeneic cells were used to quantitate the cytotoxic potential of peripheral blood mononuclear cells from healthy individuals following irradiation with a single dose of 1000 cGy on day 0, 1320 cGy of fractionated radiation (165 cGy b.i.d. x 4 days), or split-dose irradiation consisting of 1000 cGy on day 0 followed 5 or 7 days later by 500 cGy. Both irradiated and nonirradiated (control) PBMC cultures were maintained in culture with medium containing interleukin-2, immunophenotyped, and assayed for cytotoxicity from 1 to 8 days after irradiation. Single dose and fractionated-dose irradiation resulted in a progressive decline in cytotoxic capacity, with an 80% inhibition of both NK and LAK cell activity 8 days after onset of irradiation. The split dose of 500 cGy administered 7 days after a dose of 1000 cGy was found to be the most effective in eliminating NK (93% inhibition) and LAK (100% inhibition) cytotoxicity. These data indicate that split-dose irradiation may result in greater immunosuppression than single-dose or fractionated irradiation.

Malilay, G.P.; Sevenich, E.A.; Filipovich, A.H. (Univ. of Minnesota, Minneapolis (USA))

1990-09-01

249

NMR relaxation enhancement in gels polymerized and cross-linked by ionizing radiation: a new approach to 3D dosimetry by MRI.  

PubMed

A new type of tissue-equivalent medium for magnetic resonance imaging of the dose distributions produced by ionizing radiation has been developed. Agarose gel is infused with acrylamide and N,N'-methylene-bis-acrylamide (Bis) comonomers, which are readily polymerized by free radical initiators in de-aerated aqueous solutions. Polymerization and cross-linking induced locally by free radical products of water radiolysis increase the rate of water proton spin relaxation gradually up to doses of about 15 Gy. The slopes of the dose-response curves at 64 MHz are 0.015 and 0.28 s-1 Gy-1 for R1 and R2, respectively. The agarose matrix as well as the high (50% by weight) relative concentration of the cross-linker (Bis) per total comonomer limit the spread of polymerization so that the spatial distribution of the radiation dose is faithfully represented in the resultant spatial distribution of relaxation rates. The gel can be imaged with conventional magnetic resonance imaging devices with high spatial resolution and accuracy. In addition, due to the well established effect of the precipitation of insoluble agglomerates of highly cross-linked acrylamide, the optical turbidity of the gel increases gradually with the absorbed dose. This may provide an additional means of visualizing the dose distribution in three dimensions. The major advantage of the acrylamide-Bis-agarose gels over those that depend on ionic chemical dosimeters, for example, Fricke-infused gels, lies in the lack of diffusion of radiation-induced chemical changes subsequent to or concurrent with irradiation. PMID:8455435

Maryanski, M J; Gore, J C; Kennan, R P; Schulz, R J

1993-01-01

250

Application of ionizing radiation processing in biomedical engineering and microelectronics  

SciTech Connect

The applied radiation chemistry has made great contributions to the development of polymeric industrial materials by the characteristics reaction means such as crosslinking, graft copolymerization and low-temperature or solid-phase polymerization, and become a important field on peaceful use of atomic energy. A brief review on the applications of ionizing radiation processing in biomedical engineering and microelectronics is presented. The examples of this technique were the studies on biocompatible and biofunctional polymers for medical use and on resists of lithography in microelectronics.

Hongfej, H.; Jilan, W.

1988-01-01

251

Neural Grafts Attenuate Behavioral Deficits Produced by Early Radiation-Induced Hypoplasia of Fascia dentata Granule Cells.  

National Technical Information Service (NTIS)

A growing literature suggests that brain injuries, once believed to be irreversible, may now be successfully treated through the use of techniques involving neural transplantation of embryonic brain tissue. Such grafts typically exhibit growth, long-term ...

G. A. Mickley J. L. Ferguson T. J. Nemeth M. A. Mulvihill

1990-01-01

252

The 60Co-gamma ray-initiated seeded-emulsion polymerization of methyl methacrylate in the presence of waterborne polyurethane seeds  

Microsoft Academic Search

In this work, the waterborne polyurethane (WPU)\\/poly (methyl methacrylate) (PMMA) composite material was successfully prepared via 60Co-gamma ray radiation-induced seeded emulsion polymerization. The kinetic curves of the synthesis of WPU have been obtained in MMA medium and in acetone medium, respectively. The FT-IR spectra were used to investigate the grafting efficiency of the PMMA on WPU backbone.

Guixi Zhang; Zhicheng Zhang

2004-01-01

253

Skin Graft  

PubMed Central

Skin graft is one of the most indispensable techniques in plastic surgery and dermatology. Skin grafts are used in a variety of clinical situations, such as traumatic wounds, defects after oncologic resection, burn reconstruction, scar contracture release, congenital skin deficiencies, hair restoration, vitiligo, and nipple-areola reconstruction. Skin grafts are generally avoided in the management of more complex wounds. Conditions with deep spaces and exposed bones normally require the use of skin flaps or muscle flaps. In the present review, we describe how to perform skin grafting successfully, and some variation of skin grafting.

Shimizu, Ruka; Kishi, Kazuo

2012-01-01

254

Miniemulsion polymerization  

Microsoft Academic Search

Miniemulsions have some unique and desirable properties. They are far more robust to variations in the recipe or contaminant levels than conventional emulsions. Particle number was found to be less sensitive by at least an order of magnitude, to changes in initiator, water-phase retarder, and oil-phase inhibitor concentrations than macroemulsion polymerizations. This is because, unlike macroemulsion polymerization, there is no

F. J Schork; G. W Poehlein; S Wang; J Reimers; J Rodrigues; C Samer

1999-01-01

255

Stabilization of Colour of Woolenized Jute by Radiation Chemical Treatment. Final Report for the Period 1 November 1975-30 November 1977.  

National Technical Information Service (NTIS)

The radiation-induced graft polymerization of methyl methacrylate, ethyl acrylate, acrylonitrile, and venylacetate onto jute to prevent yellowing of the jute by light is reported. Samples were irradiated with a 5000 C; gamma-source at 0.1 Mrad per hour. (...

F. R. Al-Siddique

1978-01-01

256

Effects of diphenyliodonium hexafluorophosphate in the radiation-induced cationic polymerization of styrene. Formation and decay processes of styrene dimer radical cation  

SciTech Connect

The radiation-induced cationic polymerization of styrene in methylene chloride is promoted by the addition of (C/sub 6/H/sub 5/)/sub 2/IPF/sub 6/, while the polymerization is inhibited in the presence of (C/sub 6/H/sub 5/)/sub 2/ICl. The pulse radiolysis study reveals that both the yield and the lifetime of styrene dimer radical cation are increased by the addition of (C/sub 6/H/sub 5/)/sub 2/ICl. The kinetic plots for the decay of the dimer radical cation in the presence and absence of the salts show that the decay is predominantly due to the neutralization with Cl/sup -/. The lengthening of the lifetime of the dimer radical cation in the presence of (C/sub 6/H/sub 5/)/sub 2/IPF/sub 6/ is believed to be due to the stabilization toward Cl/sup -/ by the ion-pair formation with PF/sub 6//sup -/. Slow formation of the dimer radical cation was also observed in the presence of (C/sub 6/H/sub 5/)/sub 2/IPF/sub 6/, which is attributable to the oxidation of radical species by the salt followed by the charge transfer to monomer. Such a slow formation of radical cation in the presence of (C/sub 6/H/sub 5/)/sub 2/IPF/sub 6/ was confirmed with biphenyl in methylene chloride.

Mah, S.; Yamamoto, Y.; Hayashi, K.

1982-08-01

257

Cellulose Graft Copolymers  

Microsoft Academic Search

Graft copolymerization reactions of fibrous cellulose with vinyl monomers were initiated at free radical sites formed on the cellulose molecule by interaction with high-energy radiation, by reaction with Ce ions in acidic solution, or by H abstraction by ·OH radicals fromed by reaction of Fe ions with HLOz in aqueous solution. The effects of experimental conditions on the nature, half-lives,

Jett C. Arthur Jr

1970-01-01

258

Surface treatment of biomaterials by gamma and swift heavy ions grafting  

NASA Astrophysics Data System (ADS)

To date, the successful substitution of small diameter arteries by vascular grafts has not been achieved in humans. In order to reduce their thrombogenicity which remains the major obstacle, polymeric materials endowed with a specific affinity for Antithrombin III (ATIII) and thus able to catalyse the inhibition of thrombin by ATIII, as heparin does, were devised. Sulfonate and sulfonamide groups were introduced on phenyl rings belonging to styrene residues which were radiation grafted (swift heavy ions and gamma radiation) onto poly(vinylene difluoride) (PVDF) and poly(hexafluoropropylene vinylidene fluoride) (P(VDF-HFP)). Contrary to gamma radiation grafting, with swift heavy ions grafting, only small regions are modified; thus, the properties of the initial substrate are preserved. A characterization of surface topography was carried out by Scanning Electron Microscopy and Atomic Force Microscopy. The efficacy of the surface modification was monitored with respect to the total amount of bound ``heparin-like'' molecules measured by a toluidine blue assay, and the anticoagulant potential estimated by the thrombin time test.

Porté-Durrieu, M. C.; Aymes-Chodur, C.; Vergne, C.; Betz, N.; Baquey, Ch.

1999-05-01

259

Radiation-induced polymerization of 2,3-dimethyl-1,3-butadiene clathrate in deoxycholic acid  

Microsoft Academic Search

Poly(dimethylbutadiene) (PDMB) was synthesized through the inclusion polymerization technique, by ?-irradiation of a clathrate\\u000a of 2,3-dimethyl-1,3-butadiene in deoxycholic acid (DOCA) at 75, 150, 320 and 430 kGy. The resulting inclusion complexes PDMB@DOCA\\u000a were studied by FTIR spectroscopy and by thermal analysis (DTA, TGA and DTG). Pure PDMB was isolated by extracting the complex\\u000a PDMB@DOCA with ethanol. The best sample in

F. Cataldo; O. Ursini; P. Ragni; A. Rosati

2009-01-01

260

Engineering Polymeric Scaffolds for Bone Grafts  

Microsoft Academic Search

Orthopedic injuries resulting from trauma or improper development often require surgical intervention to restore natural tissue function. Currently, over one million operations are performed annually for the surgical reconstruction of bone [50]. The well-known limitations associated with autografts, allografts, and bone cements have led to the investigation of synthetic polymers as support matrices for bone tissue engineering. Polymers are long-chain

Martha W. Betz; Diana M. Yoon; John P. Fisher

261

Immobilization of quaternary ammonium salts on grafting particle polystyrene\\/SiO 2 and preliminary study of application performance  

Microsoft Academic Search

Polystyrene (PSt) was grafted on the surface of silica gel particles in the manner of “grafting from” in a solution polymerization system, and grafting particles PSt\\/SiO2 was obtained. The chloromethylation reaction of the grafted polystyrene was performed using a novel chloromethylation reagent, 1,4-bis(chloromethyoxy)butane which is un-carcinogenic, and grafting particles CMPS\\/SiO2 was gained. Subsequently, grafted CMPS was quaternized (denoted as QPS)

Baojiao Gao; Changsheng Qi; Qing Liu

2008-01-01

262

Preparation of quaternized dimethylaminoethylmethacrylate grafted nonwoven fabric for the removal of phosphate  

NASA Astrophysics Data System (ADS)

Dimethylaminoethylmethacrylate (DMAEMA) grafted polyethylene/polypropylene (PE/PP) nonwoven fabric was prepared by radiation-induced graft polymerization. Grafting conditions were optimized and about 150% DMAEMA grafted samples were used for further experiments. DMAEMA graft chains were later quaternized with dimethyl sulphate for the removal of phosphate ions. Adsorption experiments were conducted with quaternized DMAEMA grafted fabric for phosphate removal at low (0.5-25 ppm) and high phosphate concentrations (50-1000 ppm). Adsorbed phosphate amounts at pH 7 were found to be 63 mg phosphate/g polymer and 512 mg phosphate/g polymer for low (25 ppm) and high phosphate concentrations (1000 ppm) respectively showing the efficiency of the adsorbent material in removing phosphate. The pH effect on phosphate adsorption showed that the quaternized DMAEMA grafted nonwoven fabric can adsorb phosphate over a wide pH range (5.00-9.00) indicating that adsorbent material can effectively remove different forms of phosphate ions, namely H2PO4-, HPO42- and PO43- in aqueous solution at this pH range where the species exist. Competitive adsorption experiments were also carried out with two concentration levels at pH 7 to investigate the effect of competing ions. Phosphate adsorption on quaternized DMAEMA grafted nonwoven fabric was found to be higher than the other competing ions at two concentration levels. At high concentration level, the adsorption order was phosphate>nitrite>bromide>sulphate>nitrate whereas at low concentration level, the order was phosphate?sulphate>bromide>nitrite>nitrate.

Kavakl?, P?nar Akka?; Kavakl?, Cengiz; Güven, Olgun

2010-03-01

263

Telechelic polymers by living and controlled\\/living polymerization methods  

Microsoft Academic Search

Telechelic polymers, defined as macromolecules that contain two reactive end groups, are used as cross-linkers, chain extenders, and important building blocks for various macromolecular structures, including block and graft copolymers, star, hyperbranched or dendritic polymers. This review article describes the general techniques for the preparation of telechelic polymers by living and controlled\\/living polymerization methods; namely atom transfer radical polymerization, nitroxide

Mehmet Atilla Tasdelen; Muhammet U. Kahveci; Yusuf Yagci

2011-01-01

264

Silver nanoparticles in polyvinylpyrrolidone grafted natural rubber  

Microsoft Academic Search

Polyvinylpyrrolidone grafted natural rubber (PVP-g-NR) latex was used as matrix to synthesize silver nanoparticles. The average diameter of the silver nanoparticles is 4.1nm. The modified natural rubber was previously formed via in situ polymerization of N-vinyl-2-pyrrolidone (NVP) in natural rubber latex (NRL) using cumene hydroperoxide (CHP) and tetraethylenepentamine (TEPA) as a redox initiator. The evidence of PVP grafted rubber particles

N. H. H. Abu Bakar; J. Ismail; M. Abu Bakar

2010-01-01

265

Preparation of fibrous adsorbents containing amidoxime groups by radiation-induced grafting and application to uranium recovery from sea water  

SciTech Connect

Polypropylene fibers and polyethylene hollow fibers were used as trunk polymers and were irradiated by electron beams with a dose of 200 kGy under N{sub 2} atmosphere. Grafting of acrylonitrile to those irradiated fibers was carried out at 40{degree} C for different periods of time. The degree of grafting was determined as a function of time. The fibrous adsorbents containing amidoxime groups were prepared by the reaction of acrylonitrile-grafted polymers with 3% hydroxylamine in a methanol-water mixture (1:1). Distribution of copper ions complexed with amidoxime groups at various adsorption times was obtained by electron-probe X-ray microanalysis. The amidoxime groups are homogeneously distributed in the cross section of fibrous adsorbents. The fibrous adsorbents based upon polypropylene fiber of 40 {mu}m showed a remarkable kinetic behavior for Cu{sup 2+}. Even after 15 min, the adsorption capacity was 2.32 mmol Cu{sup 2+} per gram of fiber. Also, the functionalization with hydroxylamine was carried out at different conditions to compare the adsorption characteristics of the resultant adsorbents. Despite having superficially different properties (elemental microanalysis, ion-exchange capacities, adsorption capacity for UO{sup 2+}{sub 2}), the polypropylene-based fibrous adsorbents showed similar adsorption properties for uranium from sea water. The adsorption tests proved the performance of the polypropylene-based fibrous adsorbents as a promising material for uranium recovery from sea water. In addition, uranium uptake of fibrous adsorbents increased in proportion to the volume of sea water.

Kabay, N.; Katakai, A.; Sugo, T. [Takasaki Radiation Chemistry Research Establishment (Japan); Egawa, H. [Kumamoto Univ. (Japan)

1993-07-20

266

Morphology and mechanical properties of radiation-polymerized urethane-acrylates. I. Pure oligomers. [Electron beams and gamma radiation of acrylo-urethane oligomers  

SciTech Connect

The morphology of electron beam cured polyacrylo-urethane films based on polyethylene adipate and toluene diisocyanate was characterized to explain their mechanical properties. The polyacrylo-urethane films have a one-phase morphology in which the hard urethane segments and the soft polyester segments are homogeneously mixed. The films obtained from 1000-molecular-weight oligomer are hard and somewhat brittle due to their one-phase morphology in which hard glassy segments play a dominant role. The films obtained from 4600- and 6000-molecular-weight oligomers are soft and tough, once again due to their one-phase morphology in which soft rubbery segments are more effective. The original crystalline structure of 6000-molecular-weight oligomer is retained in the precrystallized ..gamma..-irradiated film, but electron-beam-irradiated films showed partial melting of the crystallites due to the heat of polymerization. The solid state polymerized films have a lower elongation, a higher modulus, and a higher breaking strength due to their crystallinity.

Wadhwa, L.H.; Walsh, W.K.

1982-02-01

267

Synthesis, Characterization, and Performance Evaluation of Polymeric HALS in Ethylene?Propylene?Diene Terpolymer (EPDM)  

Microsoft Academic Search

A polymeric hindered amine light stabilizer (HALS), wherein the hindered amine functionality was attached to the maleic anhydride graft ethylene?propylene?diene terpolymer (EPDM) was synthesized. This involves photoinduced grafting of maleic anhydride groups on unsaturated sites of EPDM, followed by incorporation of amino terminated HALS. The grafting and functionalization reactions were characterized by FTIR and C NMR spectroscopy. The surface changes

Sunil P. Lonkar; Sravendra Rana; R. P. Singh; J. Lacoste; J. L. Gardette; F. Jestin; E. Brocord

2005-01-01

268

Synthesis of arsenic graft adsorbents in pilot scale  

NASA Astrophysics Data System (ADS)

Synthesis of arsenic (As) adsorbents in pilot scale was carried out with a synthesizing apparatus by radiation-induced graft polymerization of 2-hydroxyethyl methacrylate phosphoric acid monomer (PA), which consists of phosphoric acid mono- (50%) and di- (50%) ethyl methacrylate esters onto a nonwoven cotton fabric (NCF), and following chemical modification by contact with a zirconium (Zr) solution. The apparatus which was equipped with reaction tanks, a washing tank and a pump can produce up to 0.3 m×14 m size of the As(V) adsorbent in one reaction. A degree of grafting of 150% was obtained at an irradiation dose of 20 kGy with 5% of PA solution mixed with deionized water for 1 h at 40 °C. Finally, after Zr(IV) was loaded onto a NCF with 5 mmol/L of Zr(IV) solution, the graft adsorbent for the removal of As(V) was achieved in pilot-scale. The adsorbent which was synthesized in pilot scale was evaluated in batch mode adsorption with 1 ppm (mg/l) of As(V) solution for 2 h at room temperature. As a result, the adsorption capacity for As(V) was 0.02 mmol/g-adsorbent.

Hoshina, Hiroyuki; Kasai, Noboru; Shibata, Takuya; Aketagawa, Yasushi; Takahashi, Makikatsu; Yoshii, Akihiro; Tsunoda, Yasuhiko; Seko, Noriaki

2012-08-01

269

Kinetic approach to radiation-induced grafting in the polyethylene-styrene system. IV. Comparison between high density polyethylene and low density polyethylene. [Gamma radiation  

SciTech Connect

The investigation method reported in earlier articles was applied to preirradiation methods of the reaction of low-density polyethylene (LDPE) in liquid and vapor and compared with high-density polyethylene (HDPE). Monomer concentrations during reactions and monomer feed rates were determined gravimetrically. Increasing patterns of the degree of grafting were obtained and compared. Monomer concentration during the reactions was lower in LDPE than HDPE and radical decay was more rapid in LDPE. A model calculation was applied to this experiment and a schematic explanation was attempted. The differences between the reaction mechanisms of HDPE and LDPE are explained.

Imai, M.

1981-07-01

270

Microemulsion Polymerization  

Microsoft Academic Search

Polymerization in microemulsions is reviewed. The effects of internal microstructure (oil in water, water in oil, bicontinuous) on resulting polymer morphology and characteristics are described. Aspects controlling latex particle size and composite closed cell and open cell length scales are discussed. Formulation effects on polymer functionalization are outlined.

Florentina M. Pavel

2004-01-01

271

Highly hydrophilic and low-protein-fouling polypropylene membrane prepared by surface modification with sulfobetaine-based zwitterionic polymer through a combined surface polymerization method  

Microsoft Academic Search

Poly(sulfobetaine methacrylate) [poly(SBMA)], a zwitterionic polymer, was successfully tethered in high density onto polypropylene (PP) membrane surface through a combined method consisting of UV-induced surface graft polymerization followed by surface-initiated atom transfer radical polymerization (ATRP). 2-Hydroxyethyl methacrylate (HEMA) was first immobilized onto PP membrane surface by UV-induced graft polymerization, and then each of the grafted poly(HEMA) chains, after coupled with

Yong-Hong Zhao; Kin-Ho Wee; Renbi Bai

2010-01-01

272

Biokompatible Polymere  

NASA Astrophysics Data System (ADS)

Der klinische Einsatz von synthetischen Polymeren begann in den 60-er Jahren in Form von Einwegartikeln, wie beispielsweise Spritzen und Kathetern, vor allem aufgrund der Tatsache, dass Infektionen infolge nicht ausreichender Sterilität der wiederverwendbaren Artikel aus Glas und metallischen Werkstoffen durch den Einsatz von sterilen Einwegartikeln signifikant reduziert werden konnten [1]. Die Einführung der medizinischen Einwegartikel aus Polymeren erfolgte somit nicht nur aus ökonomischen, sondern auch aus hygienischen Gründen. Wegen der steigenden Anzahl synthetischer Polymere und dem zunehmenden Bedarf an ärztlicher Versorgung reicht die Anwendung von Polymeren in der Medizin von preisgünstigen Einwegartikeln, die nur kurzzeitig intrakorporal eingesetzt werden, bis hin zu Implantaten, welche über eine längere Zeit grossen Beanspruchungen im menschlichen Körper ausgesetzt sind. Die steigende Verbreitung von klinisch eingesetzten Polymeren ist auf ihre einfache und preisgünstige Verarbeitbarkeit in eine Vielzahl von Formen und Geometrien sowie auf ihr breites Eigenschaftsspektrum zurückzuführen. Polymere werden daher in fast allen medizinischen Bereichen eingesetzt.

Ha, Suk-Woo; Wintermantel, Erich; Maier, Gerhard

273

Radiation-chemical synthesis of polypropylene fabrics with sulfonic acid functional groups  

NASA Astrophysics Data System (ADS)

A sorption-active material carrying sulfonic acid groups was synthesized by the radiation-induced graft polymerization of styrene monomer onto the surface of non-woven polypropylene fabric, followed by sulfonation of the grafted polystyrene chains. The effect of the main experimental parameters (absorbed dose, monomer concentration, reaction time) on the styrene degree of grafting was investigated. The sulfonation process with 5% chlorosulfonic acid at room temperature was investigated in detail and the optimal sulfonation conditions for the samples with a medium degree of grafting (70-140%) were determined. Densities of 3.5-5 meq/g were obtained by applying those sorption-active PP fabrics with a sulfonic acid group.

Cho, Hyun Kug; Park, Jung Soo; Han, Do Hung; Bondar, Iuliia

2011-04-01

274

Hydrolases in Polymer Chemistry: Chemoenzymatic Approaches to Polymeric Materials  

NASA Astrophysics Data System (ADS)

Lipases show high activity in the polymerization of a range of monomers using ring-opening polymerization and polycondensation. The range of polymer structures from this enzymatic polymerization can be further increased by combination with chemical methods. This paper reviews the developments of the last 5-8 years in chemoenzymatic strategies towards polymeric materials. Special emphasis is on the synthesis of polymer architectures like block and graft copolymers and polymer networks. Moreover, the combination of chemical and enzymatic catalysis for the synthesis of unique chiral polymers is highlighted.

Heise, Andreas; Palmans, Anja R. A.

275

Grafting of n-butyl acrylate with natural rubber latex film by gamma radiation: a reaction mechanism  

Microsoft Academic Search

Natural rubber latex (NRL) and n-butyl acrylate (n-BA) were blended and irradiated at various absorbed doses by gamma rays from Co-60 source at room temperature. The stabilizing effect was determined by measuring the pH and viscosity of NRL with n-BA with the storage time of five weeks. The cross-link density, swelling ratio of the radiation vulcanized rubber film were measured.

K. M. Z. Hossain; A. M. Sarwaruddin Chowdhury

2010-01-01

276

Clinical factors increasing radiation doses to patients undergoing long-lasting procedures: Abdominal stent-graft implantation  

PubMed Central

Summary Background An important negative factor of EVAR is the radiation acquired during long-lasting procedures. The aim of the study was to document the radiation doses of EVAR and to discuss potential reasons for prolongation of radiological procedures. Material/Methods Dose-area product (DAP) (Gy cm2) and air kerma (AK) (Gy) obtained during EVAR from 92 patients were analyzed retrospectively in regards to body mass index (BMI), angulations of aneurysm neck, length of aneurysm neck and occurrence of tortuosity of iliac arteries. Results Total AK for fluoroscopy differed significantly between normal BMI (373 mGy) and BMI 25–29.9 (1125 mGy) or BMI >30 (1085 mGy). Iliac artery tortuosities >45° and short aneurysm necks caused higher doses of total AK (1097 mGy and 1228 mGy, respectively) than iliac artery tortuosities <45° and long aneurysm necks (605 mGy and 720 mGy, respectively). Conclusions The main factors contributing to a high radiation dose being acquired by patients during EVAR are: BMI >25, tortuosity of iliac arteries >45° and short aneurysm necks.

Majewska, Natalia; Stanisic, Michal G.; Blaszak, Magdalena Aleksandra; Juszkat, Robert; Frankiewicz, Maciej; Krasinski, Zbigniew; Makalowski, Marcin; Majewski, Waclaw

2011-01-01

277

ON Co⁶° GAMMA RAY-INITIATED EMULSION POLYMERIZATION  

Microsoft Academic Search

A study was made of the Co⁶° gamma -ray-initiated polymerization ; of methyl methacrylate and styrene; conversion rates were measured by a ; dilatometric method. The dependence of polymerization rate on monomer ; concentration and radiation intensity was determined for each monomer. It is ; shown that the emulsion polymerization of methyl methacrylate can be described by ; accepted theories

G. J. K. Acres; F. L. Dalton

1963-01-01

278

Radiation-induced mouse chimeras: a cellular analysis of the major lymphoid compartments, factors affecting lethal graft versus host disease and host-tumor interactions  

SciTech Connect

The major lymphoid compartments of allogeneic bone marrow chimeras were evaluated for the extent of cell chimerism and distribution of Thy 1 and la bearing cells. These chimeras contained lymphoid cell primarily of donor origin. The bone marrow compartment was a mixture of host and donor origin cells. The distribution of Thy 1 and la bearing cells was similar as in normal mice. The effect of adult thymectomy alone or followed by whole-body irradiation and bone marrow reconstitution on the distribution of the Thy 1 positive cells was also investigated. Thymectomy with or without WBI and bone marrow reconstitution significantly lowered the number of Thy 1 bearing cells in the blood and spleen. The number of la bearing cells did not appear to be affected by thymectomy. The role of circulating lymphoid cells in the incidence of lethal graft versus host disease (GVHD) in radiation induced fully allogeneic mouse chimeras was studied. Mice reconstituted with allogeneic bone marrow from bled donors had a statistically lower incidence of GVHD than those reconstituted with bone marrow from unbled donors. Addition of mature peripheral lymphocytes from blood to the reconstituting bone marrow cells from bled donors reduplicated the high incidence of lethal GVHD. It was demonstrated that the bone marrow of mice not exsanguinated prior to harvesting of bone marrow contained significant numbers of peripheral contaminating cells in the harvested bone marrow. The role of suppressor cell elimination in resisting tumor growth was investigated using radiation induced mouse chimeras. Local effects of irradiation alone at the site of tumor inoculation could account for this lack of growth.

Almaraz, R.

1981-01-01

279

Graft copolymers from poly(2,6-dimethylphenylene oxide) and pivalolactone  

SciTech Connect

The copolyether-polyester system resulting from the anionic graft polymerization of pivalolactone onto poly(2,6-dimethylphenylene oxide) has been formulated with differing graft densities and graft segment lengths. Wide angle X-ray scattering studies on these materials indicated an increased crystalline order with increased PVL segments/graft for similarly annealed specimens and a decrease in such order with increasing carboxylation. 10 references.

Bell, V.L.; Wakelyn, N.T.

1988-01-01

280

Preparation and Characterization of Cotton Textile Graft Copolymers as Cation Exchanger  

Microsoft Academic Search

Acrylic Acid (AA) was graft copolymerized with cotton cellulose in fabric form to prepare poly (AA)-cotton graft copolymer cation exchanger using Fe2+\\/BrO3- redox system in aqueous medium under a nitrogen atmosphere. The effect of Fe2+, BrO3- and monomer concentrations, pH as well as time and temperature of polymerization were studied by determining the grafting parameters gravimetrically, like Graft Yield (GY

Kh. M. Mostafa

2005-01-01

281

Chain Reaction Polymerization.  

ERIC Educational Resources Information Center

The salient features and importance of chain-reaction polymerization are discussed, including such topics as the thermodynamics of polymerization, free-radical polymerization kinetics, radical polymerization processes, copolymers, and free-radical chain, anionic, cationic, coordination, and ring-opening polymerizations. (JN)

McGrath, James E.

1981-01-01

282

Fundamental and application of surface-initiated atom transfer radical polymerization for surface modification of sheets and nanoparticles  

Microsoft Academic Search

A recently developed surface grafting technique, surface-initiated atom transfer radical polymerization (ATRP), has the ability to directly graft polymer chains with controllable chain lengths, densities and functionalities from various kinds of surfaces. This thesis has two main focuses. First is to study the use of this technique in grafting monomers with special structures and functionalities. The other is to apply

Renxu Chen

2009-01-01

283

Surface Modification of PET Fabric by Graft Copolymerization with Acrylic Acid and Its Antibacterial Properties  

PubMed Central

Graft copolymerization of acrylic acid (AA) onto Poly(ethylene terephthalate) (PET) fabrics with the aid of benzoyl peroxide was carried out. The effect of polymerization parameters on the graft yield was studied. Percent grafting was enhanced significantly by increasing benzoyl peroxide (BP) concentrations up to 3.84?g/lit and then decreased upon further increase in initiator concentration. Preswelling of PET leads to changes in its sorption-diffusion properties and favors an increase in the degree of grafting. The antibiotics treated grafted fabrics showed antibacterial properties towards gram-positive and gram-negative microorganisms. FTIR and SEM were used to characterize AA-grafted polyester fabrics.

Abdolahifard, M.; Bahrami, S. Hajir; Malek, R. M. A.

2011-01-01

284

Polymer chains grafted "to" and "from" layered silicate clay platelets.  

PubMed

Polymerization of lauryl methacrylate "to" and "from" the surface of montmorillonite platelets was studied under a range of different reaction conditions. The polymerization was performed in order to achieve better organic coverage of the platelets, thus facilitating their exfoliation in the polymer matrices. For polymerization "to" the surface, a methacrylic functionality was first generated on the clay surface which was subsequently polymerized with the external lauryl methacrylate monomer. Substantial amounts of the polymer could be attached to the surface when lower polymerization temperatures and longer reaction times were used. Bulk polymerization was more effective in increasing the amount of polymer mass on the surface. In order to achieve polymerization "from" the surface, a bicationic initiator was first ionically bound on the surface followed by polymerization with lauryl methacrylate. Under the nonliving conditions, however, no significant amount of polymer could be grown from the surface. Nitroxide-mediated living polymerization was successful in eliminating suspected termination reactions leading to substantial gains in the organic mass bound to clay surfaces. Care was taken to avoid the presence of excess of unbound ammonium ions which can interfere in the grafting of polymer chains on the surface. X-ray diffraction and transmission electron microscopy in conjunction with thermogravimetric analysis confirmed the grafting of the polymer chains on the surface. PMID:17586519

Mittal, V

2007-06-27

285

Swollen polymeric complex membranes for olefin\\/paraffin separation  

Microsoft Academic Search

Swollen complex membrane of linear low density polyethylene-graft-poly(acrylic acid)-Ag+ (LLDPE-g-AA-Ag+) were studied and compared with the corresponding membranes based on silicone rubber (SR) and poly[1-(trimethylsilyl)-1-propyne] (PTMSP), such as SR-g-AA-Ag+ and PTMSP-g-AA-Ag+. The polymeric matrix was first grafted with acrylic acid (AA) and then incorporated with silver ions (Ag+) in glycerol solution for forming the swollen complex membrane. Various metal ions

Jin-Sheng Yang; Ging-Ho Hsiue

1998-01-01

286

Surface functionalization of nanodiamond particles via atom transfer radical polymerization  

Microsoft Academic Search

Ultradispersed diamond (UDD)\\/polymer brushes having excellent solution dispersibilities are prepared by atom transfer radical polymerization (ATRP) using the “grafting-from” synthesis strategy. ATRP initiators, covalently attached to oxidized surface carbon atoms of UDD aggregates using esterification chemistry, initiate polymerization of methacrylate monomers to form hydrophobic UDD\\/poly(iso-butyl methacrylate) and UDD\\/poly(tert-butyl methacrylate) polymer brushes. Acid hydrolysis of a UDD\\/poly(tert-butyl methacrylate) polymer brush affords

Lang Li; J. L. Davidson; Charles M. Lukehart

2006-01-01

287

Studies in reactive extrusion processing of biodegradable polymeric materials  

Microsoft Academic Search

Various reaction chemistries such as Polymerization, Polymer cross-linking and Reactive grafting were investigated in twin-screw extruders. Poly (1,4-dioxan-2-one) (PPDX) was manufactured in melt by the continuous polymerization of 1,4-dioxan-2-one (PDX) monomer in a twin-screw extruder using Aluminum tri-sec butoxide (ATSB) initiator. Good and accurate control over molecular weight was obtained by controlling the ratio of monomer to initiator. A screw

Sunder Balakrishnan

2006-01-01

288

Living anionic polymerization  

Microsoft Academic Search

For about 40 years living anionic polymerization has been the premier technique for the synthesis of model polymers of controlled architecture and narrow molecular weight distribution (MWD). Nowadays, despite the continuing development of new strategies for the synthesis of well-defined polymers and copolymers (e.g. group transfer polymerization, living radical polymerization, etc.), anionic polymerization continues to be the most reliable and

Kunlun Hong; David Uhrig; Jimmy W Mays

1999-01-01

289

Spectroscopic investigation of polystyrene surface grafting on natural rubber.  

PubMed

This paper investigates the structural characteristics of polystyrene (PS) grafted on a natural rubber (NR) surface using Raman scattering spectroscopy. The nitroxide-mediated radical polymerization (NMRP) technique was used to achieve the graft copolymerization of PS onto the surface of NR film using 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) as a nitroxide mediator. The reversible reaction between propagating radical and TEMPO of the NMRP process leads to a controlled radical polymerization of styrene on the NR surface. The grafting degree of PS on the NR was first measured by gravimetric methods. It was found to depend linearly on the grafting time. The characteristic signals detected by Raman scattering and by attenuated total reflection (ATR) Fourier transform infrared (FT-IR) spectroscopy provide clear evidence of the PS being grafted onto the NR. The distribution of the grafted PS on the NR substrate was determined from the Raman mapping. It is seen that the grafting occurs homogeneously over the entire surface ( approximately 40 mole % PS). The study using the Raman depth profiling technique on the original sample compared with the analysis carried out on the sample prepared by cross-sectioning led to important and comparable information regarding the uniform distribution of PS grafting inside the substrate. PMID:19215654

Prakanrat, Supinya; Phinyocheep, Pranee; Daniel, Philippe

2009-02-01

290

Thermal properties and morphology of cassava starch grafted with different content of polystyrene  

Microsoft Academic Search

The interest in replacing synthetic polymers by biodegradable materials from renewable resources is steadily increasing. In\\u000a this work, cassava starch grafted with different content of polystyrene (PS) was synthesized via free-radical polymerization\\u000a using suspension polymerization technique. Thermal data of pure starch and the grafted starch with different content of PS\\u000a were collected by simultaneous thermogravimetric (TG)–differential scanning calorimetry (DSC) setup

Kaewta Kaewtatip; Varaporn Tanrattanakul; Katalin Mészáros Szécsényi; Jelena Pavli?evi?; Jaroslava Budinski-Simendi?

2010-01-01

291

Graft Copolymerization of Furfuryl Alcohol and Cellulosic Materials  

Microsoft Academic Search

Furfuryl alcohol (FA) in aqueous medium at pH 2.0 and 90°C in presence of H2O2\\/Fe polymerized under crosslinking, without grafting to cellulosic fibers if present. Under the same conditions acid-prepolymerized furfuryl alcohol (PFA) transformed into a water-soluble polymer that grafted to cellulosic fibers (polymer load of 68%) with a negligible formation of a crosslinked homo-polymer. Decrease in the reaction temperature

Chieu Nguyen; Eugene Zavarin

1986-01-01

292

Synthesis of cationic polymer-grafted cellulose by aqueous ATRP  

Microsoft Academic Search

We describe the synthesis of cellulose fibers densely grafted with the cationic polymer poly[2-(methacryloyloxy)ethyl]-trimethylammoniumchloride (PMeDMA) through aqueous ATRP. The hydroxyl groups present on the cellulose surface were exploited to initiate the ATRP polymerization of MeDMA. We first grafted a bromide initiator, known to be an efficient initiator for ATRP, on the cellulose surface from which the polymer was then directly

O. Glaied; M. Dubé; B. Chabot; C. Daneault

2009-01-01

293

Plasma-induced polymerization for enhancing paper hydrophobicity.  

PubMed

Hydrophobic modification of cellulose fibers was conducted via plasma-induced polymerization in an attempt to graft the hydrophobic polymer chains on paper surface, this increasing the hydrophobicity of paper. Two hydrophobic monomers, butyl acrylate (BA) and 2-ethylhexyl acrylate (2-EHA), were grafted on cellulose fibers, induced by atmospheric cold plasma. Various influencing factors associated with the plasma-induced grafting were investigated. Contact-angle measurement, Fourier Transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM) were used to ascertain the occurrence of the grafting and characterized the changes of the cellulose fiber after modification. The results showed that the hydrophobicity of the modified paper sheet was improved significantly after the plasma-induced grafting. The water contact angle on the paper surface reached up to 130°. The morphological differences between modified and unmodified samples were also revealed by SEM observation. The resulting paper is promising as a green-based packaging material. PMID:23218385

Song, Zhaoping; Tang, Jiebin; Li, Junrong; Xiao, Huining

2012-10-08

294

Development of a New Polymeric Surfactant for Chemical Enhanced Oil Recovery  

Microsoft Academic Search

This work presents a new alkaline–surfactant (AS) flooding formulation that replaces and improves the traditional alkaline–surfactant–polymer (ASP) flooding slug. With the design of a cost-effective AS slug, a new series of polymeric surfactants was produced based on agriculture material. In this article, the polymeric surfactant was produced by a graft polymerization process using several surfactant-to-acrylamide ratios. This surfactant was designed

K. A. Elraies; I. M. Tan; M. T. Fathaddin; A. Abo-Jabal

2011-01-01

295

Graft irradiation abrogates graft-versus-host disease in combined pancreas-spleen transplantation  

SciTech Connect

A model of combined pancreas-spleen transplantation (PST) was studied in LBN F1 recipients of Lewis grafts in order to evaluate the efficacy of pretransplant graft irradiation in preventing lethal graft-versus-host disease (GVHD). Recipients of unmodified PST uniformly developed severe GVHD and died (MST = 16.7 +/- 3.8 days). Whole body donor irradiation with either 500 or 250 rad prevented lethal GVHD. Similarly, ex vivo graft irradiation with either 1000 or 500 rad also resulted in normal weight gain, graft function, and host survival for the 6-week study period. Conversely, delay of graft irradiation until 3 days after transplantation failed to prevent this complication (MST = 15.8 +/- 3.7 days). Recipients of irradiated grafts displayed glucose tolerance tests that were identical to those in the control group indicating that the doses of radiation employed in these experiments were not deleterious to islet function. Irradiated spleen grafts appeared histologically normal at 6 weeks after transplantation. Cells derived from these grafts failed to stimulate lymph node enlargement in a popliteal lymph node assay for GVHD, suggesting that these spleens may have become repopulated with host cells. These experiments confirm that PST has the potential to cause lethal GVHD and suggest that pretransplant graft irradiation may be used to prevent its occurrence.

Schulak, J.A.; Sharp, W.J.

1986-04-01

296

Mechanistic transformations involving living and controlled\\/living polymerization methods  

Microsoft Academic Search

This review is prepared on the occasion of the 50th anniversary of the historic discovery of living anionic polymerization by Michael Szwarc. This process enabled preparation, with good control of polymer architecture, of well-defined polymers such as block and graft copolymers, star polymers, macrocycles, and functional polymers. Transformation reactions provide a facile route to synthesis of block copolymers that cannot

Yusuf Yagci; M. Atilla Tasdelen

2006-01-01

297

Styrene\\/Acrylonitrile Graft Natural Rubber as Compatibilizer in Rubber Blends  

Microsoft Academic Search

A graft copolymer of acrylonitrile (ACN) and styrene (ST) on natural rubber (NR) was prepared by solution polymerization initiated by benzoyl peroxide. The effect of graft NR (GNR) applied as a compatibilizer for NR\\/nitrile rubber (NBR) blends on their mechanical and physical properties was investigated. The results revealed that the tensile properties and oil-swelling resistance of the blends increased with

Siriya Angnanon; Pattarapan Prasassarakich; Napida Hinchiranan

2011-01-01

298

TFC polyamide membranes modified by grafting of hydrophilic polymers: an FT-IR\\/AFM\\/TEM study  

Microsoft Academic Search

Surface modification using grafting of a hydrophilic polymer onto the membrane surface is a possible route to improving the fouling properties of polyamide thin-film composite membranes. The structure of nanofiltration (NF) and reverse osmosis (RO) membranes modified using graft polymerization of acrylic (AA) monomers was visualized and analyzed using attenuated total reflection–Fourier transform infrared spectroscopy, atomic force microscopy and transmission

Viatcheslav Freger; Jack Gilron; Sofia Belfer

2002-01-01

299

Photoactivated surface grafting from PVDF surfaces  

NASA Astrophysics Data System (ADS)

Economic and easy methods to tune surface properties of polymers as Poly(vinylidene fluoride) (PVDF) without altering bulk properties are of major interest for different applications as biotechnological devices, medical implant device… UV irradiation appears as one of the simplest, easy and safe method to modify surface properties. In the case of self-initiated grafting, it is generally assumed that the pre-treatment of the PVDF surface with UV irradiation can yield alkyl and per-oxy radicals originating from breaking bonds and capable of initiating the subsequent surface grafting polymerizations. Surprisingly, the present work shows that it is possible to obtain polymer grafting using low energetic UV-A irradiation (3.1-3.9 eV) without breaking PVDF bonds. An EPR study has been performed in order to investigate the nature of involved species. The ability of the activated PVDF surface to graft different kinds of hydrophilic monomers using the initiated surface polymerization method has been tested and discussed on the basis of ATR FT-IR, XPS and NMR HRMAS results.

Berthelot, Thomas; Le, Xuan Tuan; Jégou, Pascale; Viel, Pascal; Boizot, Bruno; Baudin, Cécile; Palacin, Serge

2011-09-01

300

Applicability of Oxidative Systems to Initiate Grafting on and Bonding of Wood  

Microsoft Academic Search

Graft polymerization techniques were applied to induce bonding in wood composites. Wood surfaces were activated with an oxidant such as hydrogen peroxide, nitric acid, peracetic acid, potassium ferricyanide or sodium dichromate. The activated wood surfaces were then chemically crosslinked with polymerizing materials such as furfuryl alcohol, ammonium lignosulfonate, mixtures of lignosulfonate with furfuryl alcohol, with formaldehyde or with maleic acid.

John L. Phllippou

1981-01-01

301

Nanocomposite proton conducting membranes based on amphiphilic PVDF graft copolymer  

Microsoft Academic Search

A novel comb-like amphiphilic graft copolymer of poly(vinylidene fluoride-co-chlorotrifluoroethylene)-graft-poly(4-styrene sulfonic acid-co-trimethoxysilyl propyl methacrylate), i.e. P(VDF-co-CTFE)-g-P(SSA-co-TMSPMA) was synthesized using an atom transfer radical polymerization (ATRP) technique. Successful synthesis and a microphase-separated\\u000a structure of the copolymer were confirmed by proton nuclear magnetic resonance (1H NMR), FTIR spectroscopy and transmission electron microscopy (TEM). This graft copolymer was combined with tetraethoxysilane\\u000a (TEOS) under acidic

Dong Kyu Roh; Jin Kyu Choi; Jong Kwan Koh; Yong Gun Shul; Jong Hak Kim

2010-01-01

302

Sulfobetaine-grafted poly(vinylidene fluoride) ultrafiltration membranes exhibit excellent antifouling property  

Microsoft Academic Search

The zwitterionic sulfobetaine methacrylate (SBMA) was grafted on the surface of poly(vinylidene fluoride) (PVDF) membrane via ozone surface activation and surface-initiated atom transfer radical polymerization (ATRP). The steady adsorption of bovine serum albumin (BSA) and ?-globulin were investigated to test the antifouling character after SBMA grafting. Hardly any albumin adsorption was observed, as the grafting density exceeded 0.4mg\\/cm2 of polySBMA.

Yen-Che Chiang; Yung Chang; Akon Higuchi; Wen-Yih Chen; Ruoh-Chyu Ruaan

2009-01-01

303

Effect of flexibility of grafted polymer on the morphology and property of nanosilica\\/PVC composites  

Microsoft Academic Search

In this study, poly(methyl methacrylate)-grafted-nanosilica (PMMA-g-silica) and a copolymer of styrene (St), n-butyl acrylate (BA) and acrylic acid (AA)-grafted-nanosilica (PSBA-g-silica) hybrid nanoparticles were prepared by using a heterophase polymerization technique in an aqueous system. The grafted polymers made up approximately 50wt.% of the resulted hybrid nanoparticles which showed a spherical and well-dispersed morphology. The silica hybrid nanoparticles were subsequently used

Aiping Zhu; Aiyun Cai; Weidong Zhou; Zhehua Shi

2008-01-01

304

The effect of maleic anhydride grafting on the flame retardation of plasma pretreated polyethylene  

Microsoft Academic Search

A rotating cylindrical-type argon plasma treatment system was used for pretreating low-density polyethylene (LDPE) to graft polar vinyl monomers. Maleic anhydride (MA) was used to graft onto plasma-treated LDPE (PLDPE) using UV-induced polymerization. The MA-grafted PLDPE (MA-g-PLDPE) was characterized by FT-IR spectra, SEM, TGA and ESCA measurement. The modified PLDPE was blended with a commercial flame-retardant additive (FR 44-94S), a

Wen-Yen Chiang; Yuan-An Ku

2002-01-01

305

Gamma-radiation-induced grafting of binary mixture of methacrylic acid and 4-vinyl pyridine onto Teflon-FEP film as an effective polar membrane for separation processes  

NASA Astrophysics Data System (ADS)

Ionic bifunctional membranes have been synthesized by grafting binary mixture of methacrylic acid (MAAc) and 4-vinyl pyridine (4-VP) onto Teflon-FEP film by pre-irradiation method. Optimum conditions pertaining to maximum percentage of grafting were evaluated as a function of different reaction parameters. Maximum percentage of grafting of binary mixture (MAAc-co-4-VP) (71.29%) was obtained at an optimum total dose of 54.48 kGy and the total concentration was 9.49 mol/L ([4-VP] = 0.07 mol/L and [MAAc ] = 9.42 mol/L) in 5 ml of water. The effect of alcohols as additives to the reaction medium on percent grafting of the binary mixture has also been studied. The membranes were characterized by FTIR spectroscopy, scanning electron microscopy and thermogravimetric analysis. Swelling studies of the membranes were performed in different solvents such as water, benzene, carbon tetrachloride and dimethyl formamide (DMF). Maximum swelling was observed in DMF with minimum swelling in benzene. Metal ion (Cu2+, Ni2+ and Fe2+) uptake studies show better affinity for Fe2+ ions. Conductance measurements in different aqueous salt solution showed that these membranes have affinity for Na+/K+ ions and Cl- ions and hence can be used in desalination/separation processes for the separation of both type of cationic and anionic ions.

Kaur, Inderjeet; Rattan, Sunita; Chauhan, Sandeep; Gupta, Nitika

2010-05-01

306

Grafting of a LLDPE using gamma irradiation  

NASA Astrophysics Data System (ADS)

In this investigation, the grafting of a commercial linear low-density polyethylene (LLDPE) with different concentrations of diethyl maleate (DEM, 5 and 15 wt.%) was carried out at different absorbed doses from a cobalt-60 source of gamma rays (0, 15, 30, 50, 100, 200 kGy). This process was performed in a decalin solution at 10% w/v to obtain a homogeneous dispersion of the monomer into the polyethylene matrix. The grafting degree was estimated by means of FTIR using a calibration curve reported in literature. Thermal properties of the functional polymers were studied by thermogravimetric analysis (TGA). Melt flow index (MFI) values were also taken. The results found indicate that the grafting degree increases as the concentration of DEM in the reaction mixture and the absorbed doses are increased upto 100 kGy, as expected. However, the behavior at higher doses is attributed to secondary reactions such as long-chain branching and/or crosslinking, which are faster than radical reactions responsible for the grafting of the DEM onto the polymeric chain. This fact was ascertained by the decrease of the MFI values as the applied irradiation was increased, irrespective of the quantity of DEM used in the grafting reaction. Therefore, in order to obtain a high grafting degree, the absorbed dose should be estimated carefully. Initial degradation temperatures of the grafted PEs decreased when the gamma irradiation dose was higher than 100 kGy. This indicates that the thermal stability decreases as higher doses are applied to the material, which is associated to branching and crosslinking. The grafting degree never exceeded 0.3 mol%, which demonstrates the low efficiency of the functionalization procedure here presented.

Catarí, E.; Albano, C.; Karam, A.; Perera, R.; Silva, P.; González, J.

2005-07-01

307

Preparing polymer brushes on polytetrafluoroethylene films by free radical polymerization  

NASA Astrophysics Data System (ADS)

Films of polytetrafluoroethylene (PTFE) were exposed to sodium naphthalenide (Na/naphtha) etchant so as to defluorinate the surface for obtaining hydroxyl functionality. Surface-initiators were immobilized on the PTFE films by esterification of 4,4?-azobis(4-cyanopentanoic acid) (ACP) and the hydroxyl groups covalently linked to the surface. Grafting of polymer brushes on the PTFE films was carried out by the surface-initiated free radical polymerization. Homopolymers brushes of methyl methacrylate (MMA) were prepared by free radical polymerization from the azo-functionalized PTFE surface. The chemical composition and topography of the graft-functionalized PTFE surfaces were characterized by X-ray photoelectron spectroscopy (XPS), attenuated total reflectance (ATR) FT-IR spectroscopy and atomic force microscopy (AFM). Water contact angles on PTFE films were reduced by surface grafting of MMA.

Sun, Wei; Chen, Yiwang; Deng, Qilan; Chen, Lie; Zhou, Lang

2006-11-01

308

Polymeric Materials for Tissue Engineering of Arterial Substitutes  

PubMed Central

Cardiovascular disease is the leading cause of mortality in the United States. The limited availability of healthy autologous vessels for bypass grafting procedures has led to the fabrication of prosthetic vascular conduits. Synthetic polymeric materials, while providing the appropriate mechanical strength, lack the compliance and biocompatibility that bioresorbable and naturally occurring protein polymers offer. Vascular tissue engineering approaches have emerged in order to meet the challenges of designing a vascular graft with long-term patency. In vitro culture techniques that have been explored with vascular cell seeding of polymeric scaffolds and the use of bioactive polymers for in situ arterial regeneration have yielded promising results. This review describes the development of polymeric materials in various tissue engineering strategies for the improvement in the mechanical and biological performance of an arterial substitute.

Ravi, Swathi; Qu, Zheng; Chaikof, Elliot L.

2009-01-01

309

Temperature-Sensitive Polypropylene Membranes Prepared by Plasma Polymerization  

SciTech Connect

PolyN-isopropylacylamide (PNIPAAm) was grafted on polypropylene (PP) microfiltration membranes using plasma polymerization. The surface of the grafted membrane was evaluated by Fourier transform infrared (FTIR) spectroscopy. Scanning electron microscopy pictures demonstrated that the PNIPAAm can be grafted either on the surface or in the pores of the membrane. The morphology of the grafted membrane can be adjusted through monomer concentration and polymerization time. Surface properties with a reversible response to temperature change were observed by measuring the dynamic contact angle. Below the LCST of PNIPAAm, the grafted PP membrane exhibited a hydrophilic surface (advancing contact angle < 40?). Above the LCST, the surface changed to hydrophobic properties (advancing contact angle > 90?). We investigated the on-off characteristics of the grafted membrane by measuring water flux through the grafted membrane at different temperatures. The water flux can be varied from 25 to 7 500 kg/m2 per hr, depending on the temperature and pressure drop. The swelling PNIPAAm chains block the pores of the microfiltration membrane, and the flux decreases (off status). The PNIPAAm chains shrink above the LCST and open the pores of the microfiltration membrane. Thus the water flux increases (on status). The effect of pressure drop on the water flux of the grafted PP membrane was discussed. The rapid and remarkable changes in the pore size of the membrane may make it possible to use the grafted PP membranes as the carrier for a drug-delivery system. They would also be used as multifunctional separation membranes, control valves, and actuators.

Liang, Liang; Shi, Ming-Kun; Viswanathan, Vilayanur V.; Peurrung, Loni M.; Young, James S.

2000-08-30

310

Polymer Grafted Janus Multi-Walled Carbon Nanotubes  

SciTech Connect

We describe a novel and facile strategy to modify the surface of carbon nanotubes (CNTs) with two chemically different polymer brushes utilizing the grafting from technique. A [4 + 2] Diels Alder cycloaddition reaction was used to functionalize multi-walled carbon nanotubes (MWNTs) with two different precursor initiators, one for ring opening polymerization (ROP) and one for atom transfer radical polymerization (ATRP). The binary functionalized MWNTs were used for the simultaneous surface initiated polymerizations of different monomers resulting in polymer grafted MWNTs that can form Janus type structures under appropriate conditions. 1H NMR, FTIR and Raman spectra showed that the precursor initiators were successfully synthesized and covalently attached on the CNT surface. Thermogravimetric analysis (TGA) revealed that the grafted polymer content varies when different monomer ratios and polymerization times are used. The presence of an organic layer around the CNTs was observed through transmission electron microscopy (TEM). Differential scanning calorimetry (DSC) proved that the glass transition (Tg) and melting (Tm) temperatures of the grafted polymers are affected by the presence of the CNTs, while circular dichroism (CD) spectra indicated that the PLLA ahelix conformation remains intact.

Priftis, Dimitrios [ORNL; Sakellariou, Georgios [ORNL; Baskaran, Durairaj [University of Tennessee, Knoxville (UTK); Mays, Jimmy [ORNL; Hadjichristidis, Nikos [University of Athens, Athens, Greece

2009-01-01

311

Oral delivery of insulin using pH-sensitive hydrogels based on polyvinyl alcohol grafted with acrylic acid\\/methacrylic acid by radiation  

Microsoft Academic Search

The pH-responsive hydrogels were studied as a drug carrier for the protection of insulin from the acidic environment of the stomach before releasing in the small intestine. Hydrogels based on poly(vinyl alcohol) networks grafted with acrylic acid or methacrylic acid were prepared via a two-step process. Poly(vinyl alcohol) hydrogels were prepared by gamma ray irradiation (50kGy) and then followed by

Young-Chang Nho; Sung-Eun Park; Hyung-Il Kim; Taek-Sung Hwang

2005-01-01

312

Synthesis of lignocellulosic polymer with improved chemical resistance through free radical polymerization.  

PubMed

Rising environmental awareness has resulted in a renewed interest in biological macromolecules obtained from renewable resources. So in view of technological significance of natural lignocellulosic polymers in numerous applications, the present study is an attempt to synthesize lignocellulosic polymers based graft copolymers using free radical polymerization. Different reaction conditions have been studied to synthesize the lignocellulosic graft copolymers. The graft copolymers have been characterized with scanning electron micrography (SEM), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The grafted samples have also been screened against different physico-chemical conditions to assess their applicability in different applications. PMID:23831536

Thakur, Vijay Kumar; Thakur, Manju Kumari; Gupta, Raju Kumar

2013-07-02

313

Basic and Engineering Studies of Radiation Induced Reactions in the Liquid Phase. Final Technical Report, June 1, 1970-May 31, 1974.  

National Technical Information Service (NTIS)

Laboratory studies reported on are ionic polymerization under superdry conditions, emulsion polymerization, and vinyl chloride polymerization. Engineering studies include the effect of moisture level on radiation-induced solution polymerization, effect of...

1978-01-01

314

Preparation and evaluation of inhalable itraconazole chitosan based polymeric micelles  

PubMed Central

Background This study evaluated the potential of chitosan based polymeric micelles as a nanocarrier system for pulmonary delivery of itraconazole (ITRA). Methods Hydrophobically modified chitosan were synthesized by conjugation of stearic acid to the hydrophilic depolymerized chitosan. FTIR and 1HNMR were used to prove the chemical structure and physical properties of the depolymerized and the stearic acid grafted chitosan. ITRA was entrapped into the micelles and physicochemical properties of the micelles were investigated. Fluorescence spectroscopy, dynamic laser light scattering and transmission electron microscopy were used to characterize the physicochemical properties of the prepared micelles. The in vitro pulmonary profile of polymeric micelles was studied by an air-jet nebulizer connected to a twin stage impinger. Results The polymeric micelles prepared in this study could entrap up to 43.2±2.27??g of ITRA per milliliter. All micelles showed mean diameter between 120–200?nm. The critical micelle concentration of the stearic acid grafted chitosan was found to be 1.58×10-2?mg/ml. The nebulization efficiency was up to 89% and the fine particle fraction (FPF) varied from 38% to 47%. The micelles had enough stability to remain encapsulation of the drug during nebulization process. Conclusions In vitro data showed that stearic acid grafted chitosan based polymeric micelles has a potential to be used as nanocarriers for delivery of itraconazole through inhalation.

2012-01-01

315

Bone grafts in dentistry  

PubMed Central

Bone grafts are used as a filler and scaffold to facilitate bone formation and promote wound healing. These grafts are bioresorbable and have no antigen-antibody reaction. These bone grafts act as a mineral reservoir which induces new bone formation.

Kumar, Prasanna; Vinitha, Belliappa; Fathima, Ghousia

2013-01-01

316

Effects of T cell depletion in radiation bone marrow chimeras. III. Characterization of allogeneic bone marrow cell populations that increase allogeneic chimerism independently of graft-vs-host disease in mixed marrow recipients  

SciTech Connect

The opposing problems of graft-vs-host disease vs failure of alloengraftment severely limit the success of allogeneic bone marrow transplantation as a therapeutic modality. We have recently used a murine bone marrow transplantation model involving reconstitution of lethally irradiated mice with mixtures of allogeneic and syngeneic marrow to demonstrate that an allogeneic bone marrow subpopulation, removed by T cell depletion with rabbit anti-mouse brain serum and complement (RAMB/C), is capable of increasing levels of allogeneic chimerism. This effect was observed in an F1 into parent genetic combination lacking the potential for graft-vs-host disease, and radiation protection studies suggested that it was not due to depletion of stem cells by RAMB/C. We have now attempted to characterize the cell population responsible for increasing allogeneic chimerism in this model. The results indicate that neither mature T cells nor NK cells are responsible for this activity. However, an assay involving mixed marrow reconstitution in an Ly-5 congenic strain combination was found to be more sensitive to small degrees of stem cell depletion than radiation protection assays using three-fold titrations of bone marrow cells. Using this assay, we were able to detect some degree of stem cell depletion by treatment with RAMB/C, but not with anti-T cell mAb. Nevertheless, if the effects of alloresistance observed in this model are considered, the degree of stem cell depletion detected by such mixing studies in insufficient to account for the effects of RAMB/C depletion on levels of allogeneic chimerism, suggesting that another cell population with this property remains to be identified.

Sykes, M.; Chester, C.H.; Sundt, T.M.; Romick, M.L.; Hoyles, K.A.; Sachs, D.H. (National Cancer Institute, Bethesda, MD (USA))

1989-12-01

317

Protein-resistant polyurethane prepared by surface-initiated atom transfer radical polymerization of water-soluble polymers  

Microsoft Academic Search

This work focused on grafting water-soluble polymers with well-controlled properties such as tuneable polymer chain length and high graft density to improve the biocompatibility of polymer surfaces via surface-initiated atom transfer radical polymerization (s-ATRP); and on gaining improved fundamental understanding of the mechanisms and factors (e.g., graft chain length and surface density of monomer units) in protein resistance of the

Zhilin Jin

2010-01-01

318

Polymeric passive laser shutters  

NASA Astrophysics Data System (ADS)

Passive laser shutters are designed to control laser pulse duration by the regulation of the Q-factor through the use of substances which change in transparency upon exposure to light. The present paper outlines the development of such a shutter composed of a radiation-resistant modified polymethyl methacrylic matrix which may be filled with different clear dyes. Experiments performed using a nickel dithiobenzyl complex as the dye are presented which show the optical density of the dye in the clear state to be proportional to the initial optical density of the shutter, and the ratio of these optical densities to depend on the purity of the materials and the extent of decay of the dye during polymerization. The feasibility of the polymer shutter in a small laser was demonstrated in experiments with a garnet laser, where no degradation was observed after 100,000 pulses, a neodymium glass laser operating for over 10,000 pulses, and a ruby laser. Potential applications of the modified polymethyl methacrylate material in other laser system components are also noted.

Gromov, D. A.; Diumaev, K. M.; Manenkov, A. A.; Masliukov, A. P.; Matiushin, G. A.; Nechitailo, V. S.; Prokhorov, A. M.

1982-10-01

319

Design of modified plastic surfaces for antimicrobial applications: Impact of ionizing radiation on the physical and mechanical properties of polypropylene  

NASA Astrophysics Data System (ADS)

Surface modification of polypropylene (PP) sheets was carried out by radiation induced graft polymerization of hydrophilic functional molecules such as N,N-dimethylacrylamide (DMA) and [2-methacryloyloxy)ethyl] trimethylammonium chloride, which is a quaternary ammonium salt (QAS).Polypropylene sheets were activated prior to the grafting reaction by using electron beam radiation. The changes in morphology, crystallinity and tensile parameters like deformation and stress at yield and deformation at break of PP after irradiation were investigated. The results showed that a minor crystalline reorganization takes place during the irradiation of PP at 100 kGy.The grafting has been observed to be strongly dependent on the monomer dilution in the reaction medium. After grafting of QAS (40%) and DMA (20%) it was possible to develop highly hydrophilic surfaces (water contact angle comprised between 30 and 41°). The surfaces of virgin, irradiated and grafted PP were studied using polarized optical microscopy (POM) and scanning electron microscopy (SEM). Spherical particles (i.e. polystyrene or silica beads) adhering to the modified samples were studied according to the surface parameters. Adhesion tests confirmed the strong influence of substrate type (mainly hydrophilicity and roughness) and to a lesser extent underlined the role of electrostatic interactions for the design of plastic surfaces for antimicrobial applications.

Riquet, Anne-Marie; Delattre, Jennifer; Vitrac, Olivier; Guinault, Alain

2013-10-01

320

COMPARISON OF MOLECULAR WEIGHT OF STARCH-GRAFT-POLY(ACRYLAMIDE) PRODUCED BY BATCH REACTION AND REACTIVE EXTRUSION  

Technology Transfer Automated Retrieval System (TEKTRAN)

Free radical polymerization of acrylamide yields a bimodal molecular weight distribution for the homopolymer. Starch-graft-poly(acrylamide) shows the same behavior for grafted poly(acrylamide) chains. This distribution is seen in both batch reaction and reactive extrusion. Conversion of monomer f...

321

Self-initiated surface grafting with poly(2-methacryloyloxyethyl phosphorylcholine) on poly(ether-ether-ketone).  

PubMed

Poly(ether-ether-ketone) (PEEK)s are a group of polymeric biomaterials with excellent mechanical properties and chemical stability. In the present study, we demonstrate the fabrication of an antibiofouling and highly hydrophilic high-density nanometer-scaled layer on the surface of PEEK by photo-induced graft polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) without using any photo-initiators, i.e., "self-initiated surface graft polymerization." Our results indicated that the diphenylketone moiety in the polymer backbone acted as a photo-initiator similar to benzophenone. The density and thickness of the poly(MPC) (PMPC)-grafted layer were controlled by the photo-irradiation time and monomer concentration during polymerization, respectively. Since MPC is a highly hydrophilic compound, the water wettability (contact angle <10 degrees) and lubricity (coefficient of dynamic friction <0.01) of the PMPC-grafted PEEK surface were considerably lower than those of the untreated PEEK surface (90 degrees and 0.20, respectively) due to the formation of a PMPC nanometer-scale layer. In addition, the amount (0.05 microg/cm(2)) of BSA adsorbed on the PMPC-grafted PEEK surface was considerably lower, that is more than 90% reduction, compared to that (0.55 microg/cm(2)) for untreated PEEK. This photo-induced polymerization process occurs only on the surface of the PEEK substrate; therefore, the desirable mechanical properties of PEEK would be maintained irrespective of the treatment used. PMID:19906420

Kyomoto, Masayuki; Moro, Toru; Takatori, Yoshio; Kawaguchi, Hiroshi; Nakamura, Kozo; Ishihara, Kazuhiko

2009-11-10

322

Chemoenzymatic synthesis and hydrogelation of amylose-grafted xanthan gums.  

PubMed

This paper reports the chemoenzymatic synthesis of an amylose-grafted xanthan gum. An amine-functionalized maltooligosaccharide was chemically introduced to xanthan gum by condensation with its carboxylates using a condensing agent to produce a maltooligosaccharide-grafted xanthan gum. Then, a phosphorylase-catalyzed enzymatic polymerization of glucose 1-phosphate from the graft chain ends on the xanthan gum derivative was performed, giving an amylose-grafted xanthan gum. Furthermore, the product formed a gel with an ionic liquid, which was converted into a hydrogel with high water content by replacement of the ionic liquid with water. The ionically cross-linked hydrogel was also provided by soaking the primary formed hydrogel in FeCl(3) aqueous solution. The mechanical properties of the resulting hydrogels were evaluated by compressive testing. PMID:21689681

Arimura, Takuya; Omagari, Yuji; Yamamoto, Kazuya; Kadokawa, Jun-ichi

2011-06-13

323

Kinetics of swelling assisted grafting of 4-vinyl pyridine onto poly(ethylene terephthalate) fibers using a benzoyl peroxide initiator  

Microsoft Academic Search

Summary Poly(ethylene terephthalate) (PET) fibers were grafted with 4-vinyl pyridine (4-VP) using benzoyl peroxide (Bz 2O 2) as initiator. Fibers were swelled in dichloroethane (DCE) for 2 h at 90 °C to promote the incorporation and the subsequent polymerization of 4-VP onto PET fibers. Variations of graft yield with time, temperature, initiator and monomer concentrations were investigated. Percent grafting was

Metin Arslan; Mustafa Yigitoglu; Oya Sanli; Halil Ibrahim Ünal

2003-01-01

324

Platelet adhesive resistance of segmented polyurethane film surface-grafted with vinyl benzyl sulfo monomer of ammonium zwitterions  

Microsoft Academic Search

Platelet from human plasma adhered on the segmented poly(ether urethane) (SPEU) film grafted with N,N-dimethyl-N-(p-vinylbenyl)-N-(3-sulfopropyl) ammonium (DMVSA) was studied. SPEU films were hydroxylated by potassium peroxosulfate (KPS) and then grafted with DMVSA using ceric ammonium nitrate (CAN) as initiator. The mixing time of hydroxylated SPEU\\/CAN and the monomer concentration effect on graft polymerization yield were determined by ATR-FTIR. Surface analysis

Jun Zhang; Jiang Yuan; Youling Yuan; Xiaopeng Zang; Jian Shen; Sicong Lin

2003-01-01

325

Surface-grafted polypeptides on flat substrates  

NASA Astrophysics Data System (ADS)

In this work, we improved the vapor deposition-polymerization (VDP) technique by re-designing a new vacuum chamber, and adding two heating plates to control the temperatures of the substrate and monomer evaporation. By optimizing the reaction parameters such as monomer amount, substrate temperature and reaction time, various polypeptides with sufficiently high molecular weight have been successfully grafted onto the solid substrates. The combination of VPD with photolithography has fabricated micro-patterned polypeptides, with geometry patternable in both lateral and vertical directions. Next, the conformations of the surface-grafted polypeptides were systematically examined. New ways have been found to switch their conformations between alpha-helix and beta-sheet, or between right-handed helix and left-handed helix. Two important ionic polypeptides, poly(L-glutamic acid) (PLGA) and poly(L-lysine) (PLL) were the focuses of this work. The conformational transitions of surface-grafted PLGA and PLL were successfully induced by pH, surfactants and ions. In addition, a surface-grafted PLGA-block-PLL copolypeptide was studied. Their unexpected pH-responsiveness was explained by the beta-sheet formation between the PLGA and PLL blocks. The orientation of the surface-grafted alpha-helical poly(gamma-benzyl L-glutamate) (PBLG) was greatly improved by a novel "solvent quenching" method, which involves treating the film sequentially with a good solvent and a poor solvent. The average tilt angle of the PBLG rods changed from 49° to 3° by applying this "quenching". Finally, a surface-grafted PLL film was used as the template to mimic the biosilicification. Silica was spontaneously synthesized from tetraethoxysilane inside the PLL film at room temperature and at neutral pH.

Wang, Yuli

326

Thermodynamics of Polymerization. I  

Microsoft Academic Search

I. THE CHILING TEMPERATURE CONCEPT A. Thermodynamic Approach The Gibbs free energy of a system at temperature T is defined as were H is the enthalpy and S the entropy of the system. The free energy change for any polymerization will be, therefore, When the polymer has a lower free energy than the initial monomer, a polymerization can occur spontaneously,

Hideo Sawada

1969-01-01

327

Molecularly imprinted polymeric membranes  

Microsoft Academic Search

Molecularly imprinted polymeric membranes have been emerged since 1990. Among various kinds of molecular imprinting studies, the application of molecular imprinting to membrane separation is still a novel investigation. In the present review paper, molecularly imprinted polymeric membranes are summarized and examined. The application of molecular imprinting to membrane separation shortly leads to high performance separation membranes.

Masakazu Yoshikawa

2001-01-01

328

The Polymerization Motor  

Microsoft Academic Search

Polymerization and depolymerization of actin filaments and microtubules are thought to generate force for movement in various kinds of cell motility, ranging from lamellipodial protrusion to chromosome segregation. This article reviews the thermodynamic and physical theories of how a nonequilibrium polymerization reac- tion can be used to transduce chemical energy into me- chanical energy, and summarizes the evidence suggesting that

Julie A. Theriot

2000-01-01

329

Step-Growth Polymerization.  

ERIC Educational Resources Information Center

Following a comparison of chain-growth and step-growth polymerization, focuses on the latter process by describing requirements for high molecular weight, step-growth polymerization kinetics, synthesis and molecular weight distribution of some linear step-growth polymers, and three-dimensional network step-growth polymers. (JN)

Stille, J. K.

1981-01-01

330

PREFACE: IUMRS-ICA 2008 Symposium, Sessions 'X. Applications of Synchrotron Radiation and Neutron Beam to Soft Matter Science' and 'Y. Frontier of Polymeric Nano-Soft-Materials - Precision Polymer Synthesis, Self-assembling and Their Functionalization'  

NASA Astrophysics Data System (ADS)

Applications of Synchrotron Radiation and Neutron Beam to Soft Matter Science (Symposium X of IUMRS-ICA2008) Toshiji Kanaya, Kohji Tashiro, Kazuo Sakura Keiji Tanaka, Sono Sasaki, Naoya Torikai, Moonhor Ree, Kookheon Char, Charles C Han, Atsushi Takahara This volume contains peer-reviewed invited and contributed papers that were presented in Symposium X 'Applications of Synchrotron Radiation and Neutron Beam to Soft Matter Science' at the IUMRS International Conference in Asia 2008 (IUMRS-ICA 2008), which was held on 9-13 December 2008, at Nagoya Congress Center, Nagoya, Japan. Structure analyses of soft materials based on synchrotron radiation (SR) and neutron beam have been developed steadily. Small-angle scattering and wide-angle diffraction techniques clarified the higher-order structure as well as time dependence of structure development such as crystallization and microphase-separation. On the other hand, reflectivity, grazing-incidence scattering and diffraction techniques revealed the surface and interface structural features of soft materials. From the viewpoint of strong interests on the development of SR and neutron beam techniques for soft materials, the objective of this symposium is to provide an interdisciplinary forum for the discussion of recent advances in research, development, and applications of SR and neutron beams to soft matter science. In this symposium, 21 oral papers containing 16 invited papers and 14 poster papers from China, India, Korea, Taiwan, and Japan were presented during the three-day symposium. As a result of the review of poster and oral presentations of young scientists by symposium chairs, Dr Kummetha Raghunatha Reddy (Toyota Technological Institute) received the IUMRS-ICA 2008 Young Researcher Award. We are grateful to all invited speakers and many participants for valuable contributions and active discussions. Organizing committee of Symposium (IUMRS-ICA 2008) Professor Toshiji Kanaya (Kyoto University) Professor Kohji Tashiro (Toyota Technological Institute) Professor Kazuo Sakurai(Kitakyushu University) Professor Keiji Tanaka (Kyushu University) Dr Sono Sasaki (JASRI/Spring-8) Professor Naoya Torikai (KENS) Professor Moonhor Ree (POSTECH) Professor Kookheon Char (Seoul National University) Professor Charles C Han (CAS) Professor Atsushi Takahara(Kyushu University) Frontier of Polymeric Nano-Soft-Materials, Precision Polymer Synthesis, Self-assembling and Their Functionalization (Symposium Y of IUMRS-ICA2008) Seiichi Kawahara, Rong-Ming Ho, Hiroshi Jinnai, Masami Kamigaito, Takashi Miyata, Hiroshi Morita, Hideyuki Otsuka, Daewon Sohn, Keiji Tanaka It is our great pleasure and honor to publish peer-reviewed papers, presented in Symposium Y 'Frontier of Polymeric Nano-Soft-Materials Precision Polymer Synthesis, Self-assembling and Their Functionalization' at the International Union of Materials Research Societies International Conference in Asia 2008 (IUMRS-ICA2008), which was held on 9-13 December 2008, at Nagoya Congress Center, Nagoya, Japan. 'Polymeric nano-soft-materials' are novel outcomes based on a recent innovative evolution in polymer science, i.e. precision polymer synthesis, self-assembling and functionalization of multi-component systems. The materials are expected to exhibit specific functions and unique properties due to their hierarchic morphologies brought either by naturally-generated ordering or by artificial manipulation of the systems, e.g., crystallization and phase-separation. The emerging precision synthesis has brought out new types of polymers with well-controlled primary structures. Furthermore, the surface and interface of the material are recognized to play an important role in the outstanding mechanical, electrical and optical properties, which are required for medical and engineering applications. In order to understand structure-property relationships in the nano-soft-materials, it is indispensable to develop novel characterization techniques. Symposium Y aimed to provide recent advances in polymer synthesis, self-assembling processes and morpholog

Takahara, Atsushi; Kawahara, Seiichi

2009-09-01

331

Radiation-grafted fluoropolymers soaked with imidazolium-based ionic liquids for high-performance ionic polymer-metal composite actuators.  

PubMed

On purpose to develop a polymer actuator with high stability in air-operation as well as large bending displacement, a series of ionic polymer-metal composites (IPMC) was constructed with poly(styrene sulfonate)-grafted fluoropolymers as ionomeric matrix and immidazolium-based ionic liquids (IL) as inner solvent. The prepared IPMC actuators exhibited greatly enhanced bending displacement compared to Nafion-based actuators. The actuators were stable in air-operation, maintaining initial displacement for up to 10(4) cycles or 24?h. Investigating the material parameters and morphology of the IPMCs, high ion exchange capacity of the ionomers resulted in high ion conductivity and robust electrode of IPMC, which synergistically contributed to the high bending performance. PMID:21567610

Lee, Jang Yeol; Wang, Hyuck Sik; Yoon, Bye Ri; Han, Man Jae; Jho, Jae Young

2010-09-06

332

Study on grafting of different types of acrylic monomers onto natural rubber by ?-rays  

NASA Astrophysics Data System (ADS)

A comparative study of various acrylic monomers for grafting onto natural rubber was done. The stability of natural rubber latex (NRL) against coagulum with monomer, mechanical properties of grafted rubbers and percent of grafting were investigated. The NRL with monomers, methylacrylate (MA), ethylacrylate (EA) and n-butylacrylate (n-BA), is unstable but it is stable with methyl methacrylate (MMA), n-butyl methacrylate (BMA) and cyclohexyl methacrylate (CHMA). The mechanical properties and degree of grafting attained a maximum at a total radiation dose of 4 kGy. The values of tensile properties of MMA and CHMA grafted rubbers are almost similar, and higher than those of BMA grafted rubbers. On the other hand, the degree of grafting for CHMA is higher than those of MMA and BMA grafted rubbers. The infrared (IR) spectra of monomer grafted natural rubber were also studied.

Dafader, N. C.; Haque, M. E.; Akhtar, F.; Ahmad, M. U.

2006-01-01

333

Radiation effect on poly ( p-sodium styrene sulphonate) of different degrees of polymerization in aqueous solution: pulse radiolysis and steady state study  

Microsoft Academic Search

Radiation induced effects on poly (p-sodium styrene sulphonate) (PSSS) of two molecular weights, namely 106 and 70,000 in aqueous solution have been investigated by steady state and pulse radiolysis (PR) techniques. The reactions of primary radicals of water radiolysis such as OH radical, eaq?, H atom, some oxidizing radicals like N3, Cl2? and SO4? and reducing species like CO2?with PSSS

Y. K. Bhardwaj; H. Mohan; S. Sabharwal; T. Mukherjee

2001-01-01

334

Entanglements of End Grafted Polymer Brushes in a Polymeric Matrix  

Microsoft Academic Search

The entanglement of a polymer brush immersed in a melt of mobile polymer chains is studied by molecular dynamics simulations. A primitive path analysis (PPA) is carried out to identify the brush\\/brush, brush\\/melt and melt\\/melt entanglements as a function of distance from the substrate. The PPA characterizes the microscopic state of conformations of the polymer chain and is ideally suited

Gary S. Grest; Robert S. Hoy

2007-01-01

335

Experimental interfascicular nerve grafting.  

PubMed

Twenty-nine adult rhesus monkeys underwent complete laceration of both tibial nerves at mid-thigh level and repair by different methods to study the relative efficacy of autogenous interfascicular nerve grafts. Sixteen animals in Group I had an interfascicular graft repair using short sural nerve autografts on one limb and fascicular repair without grafts on the other limb. Thirteen animals in Group II, after having a 1-cm segment of tibial nerve resected, had an interfascicular graft repair without tension in one limb and an epineurial repair under moderate tension in the other limb. Evoked nerve and muscle action potentials and muscle strenght in response to repetitive and tetanic stimulation were recorded as baseline values prelaceration and then on re-exploration at 4, 6, 9, or 12 months. All nerves were examined by light and electron microscopy. Electrophysiological data, particularly muscle strength response, showed non-graft repairs to be superior at 4 and 6 months of regeneration. However, by 9 and 12 months the graft repairs had caught up and were equal to the non-graft repairs. Histologically, it was observed that many axons missed the graft segments and were present in extrafascicular connective tissues. Nonetheless, enough axons regenerated to the distal nerve to explain the success of these relatively short grafts. From the results of these experiments, it is concluded that use of autogenous interfascicular grafts offers no advantage over end-to-end non-graft repair. When and end-to-end repair cannot be achieved, use of short interfascicular nerve grafts is feasible and will work. PMID:224152

Bratton, B R; Kline, D G; Coleman, W; Hudson, A R

1979-09-01

336

Stereocontrol in radical polymerization.  

PubMed

The stereospecific radical polymerization of vinyl esters, methacrylates, and alpha-substituted acrylates was studied. Fluoroalcohols, as a solvent, have remarkable effects on the stereoregularity of the radical polymerizations of vinyl acetate, vinyl pivalate, and vinyl benzoate, affording polymers rich in syndiotacticity, heterotacticity, and isotacticity, respectively. This method was successfully applied to the polymerization of methacrylates to give syndiotactic polymers. The steric repulsion between the entering monomer and the chain-end monomeric unit bound by the solvent through hydrogen bonding is important for the stereochemical control in these systems. Lewis acid catalysts, such as lanthanide trifluoromethanesulfonates and zinc salts, were also effective for the stereocontrol during the radical polymerization of methyl methacrylate, to reduce the syndiotacticity and alpha-(alkoxymethyl)acrylates to synthesize isotactic and syndiotactic polymers. Radical polymerization of the methacrylates bearing a bulky ester group, such as the triphenylmethyl methacrylate derivatives, gave highly isotactic polymers, as in the case of anionic polymerization. In addition, the control of one-handed helical conformation was attained in the radical polymerization of 1-phenyldibenzosuberyl methacrylate using chiral neomenthanethiol or cobalt(II) complexes as an additive. PMID:11893057

Habaue, S; Okamoto, Y

2001-01-01

337

Hybrid rigid/soft and biologic/synthetic materials: polymers grafted onto cellulose microcrystals.  

PubMed

Rigid nanoscale polymer rods were prepared by grafting preformed amine-terminated poly(styrene) and poly(tert-butyl acrylate) onto oxidized cellulose microcrystals. Low polydispersity polymers, grown using atom transfer radical polymerization, were characterized and purified prior to cellulose attachment. Oxidation of the cellulose microcrystal led to the formation of carboxylic acids on the surface of the microcrystals. Covalent attachment of the polymers onto the cellulose microcrystals was achieved via a carbodiimide-mediated amidation reaction. The length and diameter of the polymer-cellulose composites increased upon surface modification. Typically, polymer-cellulose composites are synthesized by a grafting-from method because it can be difficult to obtain sufficient graft density using a grafting-to preparation. However, the composites reported here comprised 60-64% grafted polymer by mass. This degree of grafting-to allowed the composite to form stable suspensions in organic solvents. PMID:21381766

Harrisson, Simon; Drisko, Glenna L; Malmström, Eva; Hult, Anders; Wooley, Karen L

2011-03-07

338

Structure and properties of silk grafted with acrylate fluoride monomers by ATRP  

NASA Astrophysics Data System (ADS)

In order to develop water repellence silk materials, silk was grafted using acrylate fluoride monomers via atom transfer radical polymerization (ATRP) method. Scanning electron microscopy (SEM) photos of the grafted silks showed significant difference from the untreated silk. FT-IR characterization of the modified silk substrate indicated that acrylate fluoride monomers were successfully grafted onto silk surface. Differential scanning calorimetry (DSC) curves indicated that the thermal stability of the grafted silk was improved. The whiteness, breaking strength, elongation at break and air permeability of the grafted silk fabrics decreased slightly compared with the control sample. Surface contact angle test and water repellency rating test showed that the water repellence of the modified silk fabrics were better than the untreated silk. Functional silk fabric with good water repellence property could be obtained by properly controlling the grafting yield, which had little effect on the intrinsic properties of silk fabric.

Li, Shiwei; Xing, Tieling; Li, Zhanxiong; Chen, Guoqiang

2013-03-01

339

Electron Beam Technologies for Preparation of Polymeric Materials Used for Waste Water Treatment, Agriculture, and Medicine  

Microsoft Academic Search

Radiation research results in the field of polymeric materials, obtained in the last few years by electron beam irradiation of aqueous solutions containing appropriate monomer mixtures, such as acrylamide, acrylic acid and vinyl acetate, are presented. Two types of polymeric flocculants for waste water treatment and three kinds of hydrogels for agriculture and medicine are described. The effects of radiation

D. Martin; M. Radoiu; M. Dragusin; R. Cramariuc; I. Indreias; C. Oproiu; S. Marghitu; A. Manea; M. Toma; V. Bestea

1999-01-01

340

Multiphase Polymeric Materials  

NSDL National Science Digital Library

Developed by a group of PhD students at the University of Southern Mississippi, the Multiphase Polymeric Materials Website presents both general information about composites and current research on multiphase polymeric materials, including information about blends, coatings, and nanocomposites. As the newest addition to Macrogalleria (described in the March 31, 1999 Scout Report for Science & Engineering), the Multiphase Polymeric Materials Website includes information on Composites in General, Composites, Characterization and Analysis, and Application. Most useful to researchers, the Application section introduces the relationship between polymer composites and component level electronics with examples such as PCB Construction, Encapsulation of Integrated Circuits, and Non-Conductive Adhesives.

341

Polymerization of Itaconic Acid.  

National Technical Information Service (NTIS)

Itaconic acid has various uses in chain copolymerization reactions, because of its two carboxylic groups and relatively good reactivity with different comonomers. As an unsaturated dicarboxylic acid it also has applications in grafting reactions and polyc...

J. Ahlgren

1990-01-01

342

Tissue Banking and Clinical Research on Radiation and Ethylene Oxide Sterilization of Tissue Grafts. Final Report for the Period June 1986-March 1987.  

National Technical Information Service (NTIS)

The research carried out in Rangoon, Burma under the Agency supported project RC4420/RB have dealt with an elucidation of the radiation interaction(s) with biomolecules such as proteins, lipids, collagens, connective tissues present in the cleaned and fre...

Pe Khin

1987-01-01

343

Ferritin-Polymer Conjugates: Grafting Chemistry and Integration into Nanoscale Assemblies  

SciTech Connect

Controlled free radical polymerization chemistry is used to graft polymer chains to the corona of horse spleen ferritin (HSF) nanocages. Specifically, poly(methacryloyloxyethyl phosphorylcholine) (polyMPC) and poly(PEG methacrylate) (polyPEGMA) chains are grafted onto the nanocages by atom transfer radical polymerization (ATRP), in which the molecular weight of the polymer grafts is controlled by the monomer-to-initiator feed ratio. PolyMPC and polyPEGMA-grafted ferritin show a generally suppressed inclusion into diblock copolymer films relative to native ferritin, and the polymer coating is seen to mask the ferritin nanocages from antibody recognition. The solubility of polyPEGMA-coated ferritin in organic solvents enables its processing with polystyrene-block-poly(ethylene oxide) copolymers, and selective integration into the PEO domains of microphase-separated copolymer structures.

Y Hu; D Samanta; S Parelkar; S Hong; Q Wang; T Russell; T Emrick

2011-12-31

344

Anionic Polymerization of Isoprene.  

National Technical Information Service (NTIS)

The polymerization of isoprene with butyllithium in cyclohexane has been studied. The initiation reaction was found to be complex; plots of conversion of butyllithium against time are sigmoidal. The order with respect to the initiator was found to be betw...

D. J. Worsfold S. Bywater

1964-01-01

345

Nanoconfinement Effect on Polymerization  

NASA Astrophysics Data System (ADS)

Ring-opening metathesis polymerization of endo-dicyclopentadidene (DCPD) with second generation Grubbs catalyst is carried out under nanoscale constraint. Differential scanning calorimetry is used to study the polymerization reaction both in the bulk and in the nanopores of controlled pore glass as a function of heating rate; the Tg of the resulting reaction product is also determined. In 110 nm-diameter pores, DCPD undergoes incomplete polymerization followed by the reverse Diels-Alder reaction to form pentadiene. Decreasing the heating rate shifts both reactions towards lower temperatures but does not avert the side reaction. In the bulk unconfined case, the reverse Diels-Alder reaction only occurs in the absence of catalyst. The glass transition temperature of the nanoconfined polymerization product is 164 C, approximately 20 C higher than the polymer prepared under bulk conditions. Reaction kinetics in bulk and nanoconfined cases will also be discussed.

Vaddey, Maitri; Simon, Sindee

2011-03-01

346

A device for a noninvasive evaluation of coronary bypass grafts  

SciTech Connect

A new device is presented for evaluating the patency of coronary bypass grafts. Bypass grafts are located within the chest cavity using a Compton Backscatter Imaging (CBI) technique that creates frontal plane tomographic images. The tomographic image pixels are mapped into computer memory and displayed. A display pointer is used to mark the position of the bypass graft. The computer uses that information to subsequently position a radiation detector, such that it looks at the location of the bypass graft within the closed chest. The patency of the graft is then evaluated by monitoring an X-ray induced iodine fluorescence transient in the graft, subsequent to a peripheral intravenous contrast injection. This imaging and graft evaluation device is relatively inexpensive and its application does not require cutdowns or catheterization. The associated radiation dose is 1/10 to 1/50 of that associated with alternative X-ray graft patency evaluation techniques. Preliminary testing has been performed on mechanical and animal models.

McInerney, J.J.; Lamser, D.G.; Herr, M.D. (Pennsylvania State Univ., Hershey, PA (United States). Dept. of Bioengineering)

1994-12-01

347

Studies on selected polymeric materials using the photoacoustic spectroscopic technique  

NASA Astrophysics Data System (ADS)

Polymethylmethacrylate—graft—polybisphenol—A-carbonate (PMMA-G-PC) with 50% grafting is synthesized. The graft co-polymerization of methylmethacrylate (0.036 mol · lit-1) onto polybisphenol—A-carbonate (0.5 g) in the presence of a redox couple formed from potassium persulphate (40 mol · lit-1) and thio-urea (30 mmol · lit-1) in aqueous nitric acid (0.18 M, 100 ml) in air at (45±2) °C for 3.0 h. Condensation of (PMMA-G-PC) with N- [p-(carboxyl phenyl amino acetic acid)] hydrazide (PCPH) affords polybisphenol-A-carbonate-graft-polymethylmethacrylate hydrazide (PCGH). The photoacoustic (PA) spectra of (PCGH) are recorded in a wavelength range from 200 nm to 800 nm at a modulation frequency of 22 Hz, and compared with those of pure polybisphenol-A-carbonate (PC), (PMMA-G-PC) and (PCPH). In the present work, a non-destructive and non-contact analytical method, namely the photoacoustic technique, is successfully implemented for optical and thermal characterization of selected polymeric materials. The indigenous PA spectrometer used in the present study consists of a 300-W xenon arc lamp, a lock-in amplifier, a chopper, a (1/8)-m monochromator controlled by computer and a home-made PA cell.

Hukum, Singh

2011-06-01

348

Free radical grafting kinetics of acrylamide onto a blend of starch/chitosan/alginate.  

PubMed

Grafting of monomer onto polymer backbone is one of the effective and accessible methods for the chemical modification of polysaccharides. Grafting of acrylamide (AAm) onto polysaccharides blend (PsB) composed of starch, chitosan and alginate has been carried out using potassium persulfate (KPS) as an initiator. The kinetics of the grafting polymerization also has been studied. The grafting parameters have been evaluated by changing the initial concentrations of AAm from 8 to 16 g, PsB from 6 to 14 g and KPS from 0.2 to 1 g. Evidence of grafting has been obtained from FTIR, XRD and TGA. The kinetics of the grafting polymerization also has been studied. The grafting rate equation of the produced hydrogel (PsB-g-AAm) hydrogel has been expressed by: Rg=k[AAm] [PsB](0.5) [KPS](0.5). The grafting rate is a first order dependence to [AAm] initial concentration and square root to [PsB] and [KPS] initial concentrations in the used concentrations range. PMID:23987368

Sorour, Mohamed; El-Sayed, Marwa; El Moneem, Nabil Abd; Talaat, Hala; Shaalan, Hayam; El Marsafy, Sahar

2013-06-03

349

Photocontrolled living polymerizations  

NASA Astrophysics Data System (ADS)

Living polymerizations involve the creation of polymer chains without significant irreversible chain transfer or chain termination. Such processes are widely used to access well-defined macromolecular materials with controlled architectures, such as block and star polymers. Although this concept was first realized for anionic polymerizations in the 1950s, many key recent advances have been made, most notably in the area of radical polymerization. Here, we report a living photopolymerization that involves photoexcited monomers. Exposure of metal-containing ferrocenophane monomers to Pyrex-filtered light from a mercury lamp (?>310 nm) or to bright sunlight in the presence of an anionic initiator leads to living polymerizations, in which the conversion and molecular weight of the resulting polymer can be controlled by the irradiation time. Photoirradiation selectively weakens the iron-cyclopentadienyl bond in the monomer, allowing the use of moderately basic and highly functional-group-tolerant initiators. The polymerization proceeds through attack of the initiator and propagating anion on the iron atom of the photoexcited monomer and, remarkably, the polymerization rate decreases with increasing temperature. Block copolymer formation is possible when the light source is alternately switched on and off in between sequential addition of different monomers, providing unprecedented, photocontrolled access to new types of functional polymers.

Tanabe, Makoto; Vandermeulen, Guido W. M.; Chan, Wing Yan; Cyr, Paul W.; Vanderark, Lawrence; Rider, David A.; Manners, Ian

2006-06-01

350

PDMS-based polyurethanes with MPEG grafts: synthesis, characterization and platelet adhesion study  

Microsoft Academic Search

Polyurethane (PU), based on poly(dimethyl siloxane) (PDMS) as a soft segment, with monomethoxy poly(ethylene glycol) (MPEG) grafted onto it, was synthesized as a new polymeric biomaterial for coating PDMS-based biomedical devices. Two different chain extenders, ethylene glycol (EG) and diethyl bis(hydroxymethyl) malonate (DBM), were used for the synthesis of PDMS-based PUs and then MPEG was grafted onto them by allophanate

Jae Hyung Park; Ki Dong Park; You Han Bae

1999-01-01

351

Preparation of polysilsesquioxane grafted thermoresponsive polymer by use of mercapto group  

Microsoft Academic Search

The polysilsesquioxane having mercapto and phenyl groups (PMPSQ) was prepared from the corresponding trimethoxysilanes by co-condensation under basic conditions. The mercapto groups on PMPSQ were utilized as the initiators for the graft polymerization of N-isopropylacrylamide (NIPAM) with the comonomer such as N,N-dimethylacrylamide (DMAA) or hydroxyethyl acrylate under UV irradiation. The grafting of the copolymers proceeded effectively to give the functionalized

Osamu Moriya; Masaki Kuga; Shin-ichi Yamamoto; Mikio Kashio; Atsuko Kamejima; Toshio Sugizaki

2006-01-01

352

Grafted polybutadiene for fast retrieval of optical information  

NASA Astrophysics Data System (ADS)

The goal of the investigations was to measure the dynamics of molecular reorientation in polybutadiene backbone based polymer grafted with photochromic thiols. Measurements were performed in a typical degenerate two- and four-wave mixing experiments, in which time constants of dynamic diffraction grating formation were determined. Holographic gratings which were inscribed in polymeric liquid crystalline films show switching times (build-up and decay) within the 20-70 ms range. An excellent reversibility of the recording-erasure process is reported.

Mysliwiec, J.; Czajkowski, M.; Miniewicz, A.; Kochalska, A.; Sedlakova, Z.; Nespurek, S.

2009-09-01

353

Blue electroluminescence from oxadiazole grafted poly(phenylene-ethynylene)s.  

PubMed

Blue poly(phenylene-ethynylene) (PPE) electroluminescence is achieved in a single layer organic light emitting device. The polymeric system consists of an oxadiazole grafted PPE, which combines the necessary charge transport properties while maintaining the desirable efficient, narrow light-emitting properties of the PPE. Incorporation of a pentiptycene scaffold within the PPE structure prevents ground-state and excited-state interactions between the pendent oxadiazole units and the conjugated backbone. PMID:16089495

Breen, Craig A; Rifai, Sandra; Bulovi?, Vladimir; Swager, Timothy M

2005-08-01

354

Preparation of polyimide composite membranes grafted by electron beam irradiation  

Microsoft Academic Search

In this study, the preparation of polyimide composite membranes was investigated by the electron beam (EB) irradiation method. The asymmetric polyimide membranes as substrates were prepared on the non-woven fabric by the phase inversion process. Electron beam irradiation was done on the polyimide membrane using the EB irradiation equipment with low acceleration voltage (50keV) in the nitrogen atmosphere. Graft polymerization

H Yanagishita; J Arai; T Sandoh; H Negishi; D Kitamoto; T Ikegami; K Haraya; Y Idemoto; N Koura

2004-01-01

355

UV and electron beam-induced cationic polymerization  

NASA Astrophysics Data System (ADS)

This paper describes the basic photochemistry which has led to the development of rapid, efficient photoinitiators for UV-induced cationic polymerizations. These polymerizations are now widely employed in UV curing processes for such applications as coatings, adhesives and printing inks. The use of photosensitizers has enabled the extension of light-induced cationic polymerizations to the visible wavelength regions as well. Electron-beam irradiation is also capable of mediating the decomposition of cationic photoinitiators. The mechanism of this reaction involves reduction of the onium salt initiator by radicals generated by e-beam induced primary bond cleavage reactions. Rapid, efficient e-beam induced polymerizations at very low doses can be achieved through the use of specially designed monomers. The use of low energy electron beam radiation for thin film applications and high energy radiation to fabricate high performance carbon fiber reinforced epoxy resin matrix composites are described.

Crivello, James V.

1999-05-01

356

Synthesis of polycaprolactone-grafted microfibrillated cellulose for use in novel bionanocomposites--influence of the graft length on the mechanical properties.  

PubMed

In the present work, microfibrillated cellulose (MFC) made from bleached sulfite softwood dissolving pulp was utilized to reinforce a poly(?-caprolactone) (PCL) biopolymer matrix. To improve the dispersibility of the hydrophilic MFC in the nonpolar matrix and the interfacial adhesion in the composite material, we covalently grafted the MFC with PCL via ring-opening polymerization (ROP) of ?-caprolactone (?-CL). To be able to investigate the effect of the PCL graft length on the mechanical properties of the composite material, we performed ROP to different molecular weights of the grafts. Bionanocomposites containing 0, 3, and 10 wt % MFC were prepared via hot pressing using both unmodified and PCL grafted MFC (MFC-g-PCL) as reinforcement. PCL grafting resulted in improved dispersion of the MFC in a nonpolar solvent and in the PCL matrix. The mechanical testing of the biocomposites showed an improvement in the mechanical properties for the PCL grafted MFC in comparison to ungrafted MFC. It was also shown that there was an impact on the mechanical properties with respect to the PCL graft lengths, and the strongest biocomposites were obtained after reinforcement with MFC grafted with the longest PCL graft length. PMID:21473594

Lönnberg, Hanna; Larsson, Karolina; Lindström, Tom; Hult, Anders; Malmström, Eva

2011-05-04

357

Preservation of platelet function on 2-methacryloyloxyethyl phosphorylcholine-graft polymer as compared to various water-soluble graft polymers.  

PubMed

The chemical structures of water-soluble polymers grafted onto PE surfaces affect platelet function when the platelets contact the polymer surfaces. To improve our understanding of this effect, this study sought to control the blood/materials interaction on the surfaces of polyethylene (PE) by grafting with various water-soluble polymers. Such polymers as poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), poly(acrylamide) (PAAm), poly(N-vinylpyrrolidone) (PVPy), and poly[monomethacryloyl poly(ethylene glycol)] (PMPEG) were grafted on low-density PE sheets by photoinduced graft polymerization. Both the PE bags modified with water-soluble polymers and those nonmodified were prepared by heat processing. Activation of platelets after storage in the PE bags was evaluated by measuring the cytoplasmic free calcium ion concentration ([Ca(2+)]i). The concentration of [Ca(2+)]i of platelets in contact with the PE surface grafted with PMPC was the same as that of native platelets and significantly less than that in contact with other PE surfaces grafted with water-soluble polymers. The number of adherent platelets was effectively decreased on PE surfaces grafted with PMPC and PMPEG, as compared with nontreated PE. The aggregation ability of platelets was also measured after storage of platelet-rich plasma in the PE bags. The PE surface grafted with PMPC effectively maintained aggregation ability as compared with both the nontreated PE and with PE grafted with PAAm, PVPy, and PMPEG. It was concluded that for preserving platelet function, PMPC was the most effective of these water-soluble polymers used for surface modification. PMID:11416851

Iwasaki, Y; Nakabayashi, N; Ishihara, K

2001-10-01

358

INHIBITING THE POLYMERIZATION OF NUCLEAR COOLANTS  

DOEpatents

>The formation of new reactor coolants which contain an additive tbat suppresses polymerization of the primary dissoclation free radical products of the pyrolytic and radiation decomposition of the organic coolants is described. The coolants consist of polyphenyls and condensed ring compounds having from two to about four carbon rings and from 0.1 to 5% of a powdered metal hydride chosen from the group consisting of the group IIA and IVA dispersed in the hydrocarbon.

Colichman, E.L.

1959-10-20

359

Preparation of Water-Insoluble Antibacterial Materials with Surface-Grafted Material PSt\\/SiO 2 and Their Antibacterial Activity  

Microsoft Academic Search

Styrene (St) was graft-polymerized onto the surfaces of micro-sized silica gel particles, and the surface-grafted composite\\u000a particles PSt\\/SiO2 were obtained. With the surface-grafted composite particles PSt\\/SiO2 as a starting material, water-insoluble antibacterial materials with quaternary ‘onium’ salt-type were synthesized via two\\u000a polymer reaction steps. The grafted polystyrene was first chloromethylated, resulting in grafted particles CMPS\\/SiO2, and then quaterisation (QN) and

Baojiao GaoQing; Qing Liu; Yanbin Li

2010-01-01

360

Grafting in Arabidopsis.  

PubMed

Grafting provides a simple way to generate chimeric plants with regions of different genotypes and thus to assess the cell autonomy of gene action. The technique of grafting has been widely used in other species, but in Arabidopsis, its small size makes the process rather more demanding. However, there are now several well-established grafting procedures available, which we described here, and their use has already contributed greatly to understanding of such processes as shoot branching control, flowering, disease resistance, and systemic silencing. PMID:24057364

Bainbridge, Katherine; Bennett, Tom; Crisp, Peter; Leyser, Ottoline; Turnbull, Colin

2014-01-01

361

Bullae in skin grafts.  

PubMed

We describe eight patients with grafted leg ulcers, in whom subepidermal bullous lesions appeared after 4-8 weeks either at the donor or the grafted site. The blisters were seen in the centre as well as just outside the graft. They remained for some days and then disappeared. Histology revealed a normal epidermis and a dermis with a moderate lymphocytic infiltration around the capillaries. No clinical signs of pemphigoid were found and friction does not seem to have been a contributing factor. We have at present no explanation for the appearance of the blisters. PMID:6380561

Baran, R; Juhlin, L; Brun, P

1984-08-01

362

Supramolecular polymeric hydrogels.  

PubMed

The supramolecular crosslinking of polymer chains in water by specific, directional and dynamic non-covalent interactions has led to the development of novel supramolecular polymeric hydrogels. These aqueous polymeric networks constitute an interesting class of soft materials exhibiting attractive properties such as stimuli-responsiveness and self-healing arising from their dynamic behaviour and that are crucial for a wide variety of emerging applications. We present here a critical review summarising the formation of dynamic polymeric networks through specific non-covalent interactions, with a particular emphasis on those systems based on host-guest complex formation, as well as the characterisation of their physical characteristics. Aqueous supramolecular chemistry has unlocked a versatile toolbox for the design and fine-tuning of the material properties of these hydrogels (264 references). PMID:22890548

Appel, Eric A; del Barrio, Jesús; Loh, Xian Jun; Scherman, Oren A

2012-08-13

363

Photoradiation processes in combined polymeric materials  

NASA Astrophysics Data System (ADS)

The methods of ESR, optical and mass-spectroscopy have been used to study the formation and decay of active intermediates, radiation and photoradiation gas evolution in a series of combined polymeric materials. The investigated samples were films of polyimide (PI), one- or two-side coated PI-fluoroplast, poly(ethylene terephthalate) (PET), PET coated with polyacryl on both sides, etc. Different coatings and polymeric substrates have been established to produce a mutual effect on the radiation- and photo-induced transformations of the combined polymers at the stage of radical formation and gas evolution. Thus, /?-irradiation of PI-fluoroplast films at 300 K intensifies the radiation-chemical processes in the fluorinated coatings, namely, the radiation-chemical yield of macroradicals in the coatings is several times higher than that in fluoro-containing polymers. In the PET film coated with polyacryl the yield of macroradicals related to polyacrylic acid is significantly lower than the value generally cited in the publications. A mutual effect of the coatings and substrates on the radiation and photoradiation-induced gas evolution is even more noticeable. Thus, a gas mixture of the PI-fluoroplast film contains lower amounts of carbon oxide and fluorinated products and no hydrogen at all. The interphase processes, distortion of the boundary layer structure, electronic equilibrium, mutual effect of the evolved gases, etc. can account for the reasons of such non-additivity.

Zhdanov, G. S.; Klinshpont, E. R.; Iskakov, L. I.

2001-12-01

364

Elastic Energy Driven Polymerization  

PubMed Central

We present a molecular system where polymerization is controlled externally by tuning the elastic energy of the monomers. The elastic energy, provided by a DNA molecular spring, destabilizes the monomer state through a process analogous to domain swapping. This energy can be large (of ?10 kT) and thus drive polymerization at relatively low monomer concentrations. The monomer-dimer equilibrium provides a measurement of the elastic energy of the monomer, which in this construction appears limited by kink formation in the DNA molecular spring, in accord with previous theoretical and experimental investigations of the elasticity of sharply bent DNA.

Wang, Andrew; Zocchi, Giovanni

2009-01-01

365

Encapsulation by Miniemulsion Polymerization  

NASA Astrophysics Data System (ADS)

The miniemulsion technique offers the possibility for the encapsulation of different materials, ranging from liquid to solid, from organic to inorganic, and from molecularly dissolved to aggregated species into polymeric nanoparticles or nanocapsules. Using this technique, a wide variety of novel functional nanomaterials can be generated. This review focuses on the preparation of functional nanostructures by encapsulating organic or inorganic material in polymeric nanoparticles. The examples demonstrate the possibilities to protect the encapsulated material as dyes, pigments, fragrances, photo-initiators, drugs, magnetite, or even DNA, use them as marker systems (dyes, magnetite), or create nanoparticles with completely new properties.

Landfester, Katharina; Weiss, Clemens K.

366

High stability of thermoresponsive polymer-brush-grafted silica beads as chromatography matrices.  

PubMed

Thermo-responsive chromatography matrices with three types of graft architecture were prepared, and their separation performance and stability for continuous use were investigated. Poly(N-isopropylacrylamide)(PIPAAm) hydrogel-modified silica beads were prepared by a radical polymerization through modified 4,4'-azobis(4-cyanovaleric acid) and N,N'-methylenebisacrylamide. Dense PIPAAm brush-grafted silica beads and dense poly(N-tert-Butylacrylamide (tBAAm)-b-IPAAm) brush-grafted silica beads were prepared through a surface-initiated atom transfer radical polymerization (ATRP) using CuCl/CuCl(2)/ Tris(2-(N,N-dimethylamino)ethyl)amine (Me(6)TREN) as an ATRP catalytic system and 2-propanol as a reaction solvent. Dense PIPAAm brush-grafted silica beads exhibited the highest separation performance because of their strong hydrophobic interaction between the densely grafted well-defined PIPAAm brush on silica-bead surfaces and analytes. Using an alkaline mobile phase, dense themoresponsive polymer brushes, especially having a hydrophobic basal layer, exhibited a high stability for continuous use, because polymer brush on the silica bead surfaces prevented the access of water to silica surface, leading to the hydrolysis of silica and cleavage of grafted polymers. Thus, the precisely modulating graft configuration of thermoresponsive polymers provided chromatography matrices with a high separation efficiency and stability for continuous use, resulting in elongating the longevity of chromatographic column. PMID:22452297

Nagase, Kenichi; Kobayashi, Jun; Kikuchi, Akihiko; Akiyama, Yoshikatsu; Kanazawa, Hideko; Okano, Teruo

2012-03-27

367

Hydrophobic grafted and cross-linked starch nanoparticles for drug delivery.  

PubMed

The synthesis of modified hydrophobic starch nanoparticles using long chain fatty acids was accomplished. Grafting of fatty acid on the starch was done using potassium persulphate as catalyst and the formation of graft polymer was confirmed by FTIR spectra. The thermal properties of the native and grafted starch were investigated using simultaneous TG-DTA and DSC. The graft polymerization was found to be depending on the temperature and the duration of the reaction. The modified starch nanoparticles were cross-linked with sodium tripoly phosphate for better stabilization. Morphology of the grafted starch nanoparticles was studied by SEM and AFM. Drug-loading and the controlled release of the drug from the nanoparticles was studied using indomethacin as model drug. PMID:17278045

Simi, C K; Emilia Abraham, T

2007-02-04

368

Ozone-initiated histidine polymerization  

Microsoft Academic Search

The ozone-initiated histidine polymerization is found by spectroscopic methods. The structural characteristics of a polymer, as well as the kinetics and conditions of its formation are defined. The reaction scheme of the histidine polymerization is proposed.

L. K. Gerasimova; B. A. Tatarinov; N. N. Khovratovich; V. P. Khrapovitsky

1985-01-01

369

Rapid synthesis of graft copolymers from natural cellulose fibers.  

PubMed

Cellulose is the most abundant natural polysaccharide polymer, which is used as such or its derivatives in a number of advanced applications, such as in paper, packaging, biosorption, and biomedical. In present communication, in an effort to develop a proficient way to rapidly synthesize poly(methyl acrylate)-graft-cellulose (PMA-g-cellulose) copolymers, rapid graft copolymerization synthesis was carried out under microwave conditions using ferrous ammonium sulfate-potassium per sulfate (FAS-KPS) as redox initiator. Different reaction parameters such as microwave radiation power, ratio of monomer, solvent and initiator concentrations were optimized to get the highest percentage of grafting. Grafting percentage was found to increase with increase in microwave power up to 70%, and maximum 36.73% grafting was obtained after optimization of all parameters. Fourier transforms infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA/DTA/DTG) analysis were used to confirm the graft copolymerization of poly(methyl acrylate) (PMA) onto the mercerized cellulose. The grafted cellulosic polymers were subsequently subjected to the evaluation of different physico-chemical properties in order to access their application in everyday life, in a direction toward green environment. The grafted copolymers demonstrated increased chemical resistance, and higher thermal stability. PMID:23987417

Thakur, Vijay Kumar; Thakur, Manju Kumari; Gupta, Raju Kumar

2013-07-08

370

Synthesis and characterization of nanocomposite organic/inorganic hybrid materials using living cationic polymerization  

NASA Astrophysics Data System (ADS)

A series of novel chlorosilyl functional initiators have been prepared and applied for the first time in the living cationic polymerization of isobutylene (IB). Well-defined polyisobutylenes (PIBs) carrying mono-, di-, and trichlorosilyl head-group, and a tert-chloro end-group were synthesized using newly designed silyl-functional initiators in conjunction with TiCl4 in Hex:MeCl (60:40, v:v) at -80°C. End-group analysis by 1H NMR spectroscopy verified the product structure and the survival of the Si-Cl head-groups during the polymerization. The chlorosilyl functional initiators and chlorosilyl functional PIBs have been employed for the synthesis of PIB brushes on planar silicate substrates by the "grafting from" and "grafting to" techniques. Structurally well-defined polymer/inorganic nanocomposites were prepared by surface-initiated living cationic polymerization of isobutylene (IB). The living cationic polymerization of IB was initiated from initiators self-assembled on the surface of silica nanoparticles in the presence of additional soluble "free initiator" with TiCl4 in hexanes/CH3Cl (60/40, v/v) at -80°C. The polymerization displayed the diagnostic criteria for living cationic polymerization and provided densely grafted polymers of controlled molecular weight with an approximate graft density of 3.3 chains/nm 2. The surface-initiated polymerization of IB without added "free initiator" also yielded grafted polymer chains with good molecular weight control and narrow molecular weight distribution (Mw/M n). A series of novel hybrid poly(styryl-POSS), poly(isobutylene- b-(styryl-POSS)), and poly(isobutylene-b-(styryl-POSS)- b-isobutylene) are synthesized and characterized. Living cationic polymerization of styryl-POSS macromer was carried out using the 1-chloro-1-(4-methyphenyl)ethane (p-MeStCl)/TiCl4/MeChx:CH3Cl (60:40, v:v)/-80°C system in the presence of DTBP. Using these conditions, we have synthesized AB diblock, and ABA linear triblock copolymers containing polyisobutylene (PIB)-based rubbery mid block (B) with amorphous glassy poly(styryl-POSS) end blocks (A) by living cationic polymerization using sequential monomer addition. Well-defined PIB-b-P(styryl-POSS) and PIB- b-P(styryl-POSS)-b-PIB have been successfully prepared. The styryl-POSS based hybrid polymers were characterized by thermogravimetry and GPC measurements. (Abstract shortened by UMI.)

Kim, Iljin

371

Smart Polymeric Materials  

Microsoft Academic Search

Smart polymeric materials respond with a considerable change in their properties to small changes in their environment. Environmental stimuli include temperature, pH, chemicals, and light. “Smart” stimuli-sensitive materials can be either synthetic or natural. This review discusses the application of smart materials as tools to solve biological problems such as bioseparation, drug delivery, biosensor design, tissue engineering, protein folding, and

Ipsita Roy; Munishwar Nath Gupta

2003-01-01

372

Polymerized Asphalt Emulsion.  

National Technical Information Service (NTIS)

It has been claimed that polymerized asphalt emulsion has outstanding characteristics of elasticity, adhesion, and cohesion which allows its use in seal coats in high speed, high volume roads, such as interstate highways. Another use would be on a lower c...

S. Q. Kidd

1990-01-01

373

Variable Effect during Polymerization  

ERIC Educational Resources Information Center

|An experiment performing the polymerization of 3-methylthiophene(P-3MT) onto the conditions for the selective electrode to determine the catechol by using cyclic voltammetry was performed. The P-3MT formed under optimized conditions improved electrochemical reversibility, selectivity and reproducibility for the detection of the catechol.|

Lunsford, S. K.

2005-01-01

374

Flame retardant polymeric materials  

SciTech Connect

The flame retardation of polyolefins is the focus of this volume. Methods for reduction of smoke and experimental evaluation of flammability parameters for polymeric materials are discussed. The flammability evaluation methods for textiles and the use of mass spectrometry for analysis of polymers and their degradation products are also presented.

Lewin, M.; Atlas, S.M.; Pearce, E.M.

1982-01-01

375

Synthesis of Novel Four Armed PE-PCL Grafted Superparamagnetic and Biocompatible Nanoparticles.  

PubMed

Novel biocompatible polymer immobilized superparamagnetic nanoparticles (MNP) are prepared by grafting four armed pentaerythritol poly(?-polycaprolactone) (PE-PCL) onto silane modified MNP. The MNPs are synthesized by hydrothermal process and its modification using (3-aminopropyl)trimethoxysilane (TMAS) coating is done by the sol-gel technique. The pentaerythritol (PE) initiated ring-opening polymerization (ROP) is carried out to prepare four armed PE-PCL. The reaction is shown to follow first order kinetics. The structure of PE-PCL is confirmed by NMR spectrum and MALDI-TOF analysis. The in situ grafting of PE-PCL onto modified MNP has been carried out by using 4,4'-methylenediphenyl diisocyanate (MDI) as an intermediate linker. The grafting density as determined by TGA analysis has been found to be significantly higher than previously reported linear PCL grafted MNPs in the literature. This leads to uniform dispersion of grafted MNPs which still is a challenging task in contemporary research. The effective dispersion of MNP into PE-PCL matrix is analyzed by HRTEM. The saturation magnetization of the PE-PCL grafted MNPs is significantly high and this can be tailored further by varying the grafting density. The biocompatibility of polymer grafted nanoparticles is confirmed by MTT assay using HeLa cell line. The superparamagnetic and biocompatible novel PE-PCL grafted MNP so prepared would have manifold potential applications including in therapy and targeted drug delivery. PMID:24041315

Panja, Sudipta; Saha, Biswajit; Ghosh, S K; Chattopadhyay, Santanu

2013-09-27

376

Preparation and characterization of poly(acrylic acid)-hydroxyethyl cellulose graft copolymer.  

PubMed

Poly(acrylic acid) hydroxyethyl cellulose [poly(AA)-HEC] graft copolymer was prepared by polymerizing acrylic acid (AA) with hydroxyethyl cellulose (HEC) using potassium bromate/thiourea dioxide (KBrO(3)/TUD) as redox initiation system. The polymerization reaction was carried out under a variety of conditions including concentrations of AA, KBrO(3) and TUD, material to liquor ratio and polymerization temperature. The polymerization reaction was monitored by withdrawing samples from the reaction medium and measuring the total conversion. The rheological properties of the poly(AA)-HEC graft copolymer were investigated. The total conversion and rheological properties of the graft copolymer depended on the ratio of KBrO(3) to TUD and on acrylic acid concentration as well as temperature and material to liquor ratio. Optimum conditions of the graft copolymer preparation were 30 mmol KBrO(3) and 30 mmol TUD/100g HEC, 100% AA (based on weight of HEC), duration 2h at temperature 50 °C using a material to liquor ratio of 1:10. PMID:22840022

Abdel-Halim, E S

2012-06-19

377

pH-sensitive starch hydrogels via free radical graft copolymerization, synthesis and properties  

Microsoft Academic Search

Natural polymers are considered high value polymeric materials because of their potential as biocompatible materials with medical applications. The chemical modification of natural polymers by grafting has received considerable attention in recent years because of the wide variety of monomers available. As the first part of a continued research on conversion of carboxymethyl starch (CMS) to useful biopolymer-based materials, large

Mohammad Reza Saboktakin; Abel Maharramov; Mohammad Ali Ramazanov

2009-01-01

378

New graft copolymers of hyaluronic acid and polylactic acid: Synthesis and characterization  

Microsoft Academic Search

New graft copolymers have been synthesized, using hyaluronic acid (HA) as a hydrophilic backbone and polylactic acid (PLA) as an aliphatic polyester in order to obtain new polymeric derivatives of HA able to hydrophobically associate in an aqueous medium. Hyaluronic acid with low molecular weight was made soluble in organic solvent by transformation to its tetrabutylammonium (TBA) salt. Using the

Fabio Salvatore Palumbo; Giovanna Pitarresi; Delia Mandracchia; Giuseppe Tripodo; Gaetano Giammona

2006-01-01

379

Nanostructural surface engineering of grafted polymers on inorganic oxide substrates for membrane separations  

NASA Astrophysics Data System (ADS)

Nanostructural engineering of inorganic substrates by free radical graft polymerization was studied with the goal of developing new membrane materials for pervaporation. Graft polymerization consisted of modification of surface hydroxyls with vinyl trimethoxysilane, followed by solution graft polymerization reaction using either vinyl acetate (VAc) or vinyl pyrrolidone (VP). The topology of the modified surfaces was studied by atomic force microscopy (AFM) on both atomically smooth silicon wafer substrates and microporous inorganic membrane supports in order to deduce the effects of modification on the nanostructural properties of the membrane. While unmodified wafers showed a root-mean-square (RMS) surface roughness of 0.21 +/- 0.03 nm, roughness increased to 3.15 +/- 0.23 nm upon silylation. Under poor solvent conditions (i.e., air), surfaces modified with higher poly(vinyl acetate) (PVAc) or poly(vinyl pyrrolidone) (PVP) polymer graft yields displayed lateral inhomogeneities in the polymer layer. Although RMS surface roughness was nearly identical (0.81--0.85 nm) for PVAc-modified surfaces grafted at different monomer concentrations, the skewness of the height distribution decreased from 2.22 to 0.78 as polymer graft yield increased from 0.8 to 3.5 mg/m2. The polymer-modified surfaces were used to create inorganic pervaporation membranes consisting of a single macromolecular separation layer formed by graft polymerization. PVAc grafted silica membranes (500A native pore size) were found selective for MTBE in the separation of 0.1--1% (v/v) MTBE from water, achieving MTBE enrichment factors as high as 371 at a permeate flux of 0.38 l/m2 hr and a Reynolds number of 6390; however, these membranes could not separate anhydrous organic mixtures. Pervaporative separation of methanol/MTBE mixtures was possible with PVAc and PVP-modified alumina supports of 50A native pore size, where the separation layer consisted of grafted polymer chains with estimated radius of gyration 4.5--6.8 times larger than the membrane pore radius. Methanol separation factors for the PVP and PVAc-grafted alumina pervaporation membranes reached values of 26 and 100 (respectively) at total permeate fluxes of 0.055--1.26 kg/m 2 hr and 0.55--6.19 kg/m2 hr. The present study demonstrated that selective pervaporation membranes for separation of both organic/organic and organic/aqueous mixtures can be effectively designed by careful selection of the surface-grafted polymer chain density and the ratio of the polymer chain size to the native support pore size.

Yoshida, Wayne Hiroshi

380

In Vivo Regenerative Properties of Coralline-Derived (Biocoral) Scaffold Grafts in Human Maxillary Defects: Demonstrative and Comparative Study with Beta-Tricalcium Phosphate and Biphasic Calcium Phosphate by Synchrotron Radiation X-Ray Microtomography.  

PubMed

BACKGROUND: In recent years, there has been interest on the fabrication of systems using particulates or block-based approach for bone tissue engineering (TE) scaffolds, possessing porous interconnected structures. In fact, these particular morphologies greatly increase the surface area for more chemical and biological reactions to take place. PURPOSE: This study was designed to demonstrate the unique capability of the synchrotron radiation x-ray microtomography (micro-CT) in offering an advanced characterization of coralline-derived (Biocoral) biomaterials placed in human maxillary defects as it allows, in a nondestructive way, a complete, precise, and high-resolution three-dimensional analysis of their microstructural parameters. Moreover, the comparison between Biocoral and other biomaterials was explored to understand the mechanism of their biological behavior as bone substitute. MATERIALS AND METHODS: Implant survival, bone regeneration, graft resorption, neovascularization, and morphometric parameters (including anisotropy and connectivity index of the structures) were evaluated by micro-CT in Biocoral and the other biomaterials after 6 to 7 months from implantation in human maxillary bone defects. RESULTS: After the in vivo tests, a huge amount of bone was detected in the retrieved Biocoral-based samples, coupled with a good rate of biomaterial resorption and the formation of a homogeneous and rich net of new vessels. The morphometric parameters were comparable to those obtained in the biphasic calcium phosphate-based control, with the exception of the connectivity index for which this control exhibited the most well-connected structure. This last result, together with those referred to the poor performances of the ?-tricalcium phosphate block-based sample, suggests that the particular scaffold morphology may play a role in the hunt the optimal scaffold structure to be implanted. CONCLUSION: In this limited study, implant success rate seems not strictly dependent on the biomaterial that is used, but on the scaffold morphology. Micro-CT technique was demonstrated to play a fundamental role in advanced characterization of bone TE constructs. PMID:23350548

Giuliani, Alessandra; Manescu, Adrian; Larsson, Emanuel; Tromba, Giuliana; Luongo, Giuseppe; Piattelli, Adriano; Mangano, Francesco; Iezzi, Giovanna; Mangano, Carlo

2013-01-25

381

Surface-grafted polymers from electrodeposited macroprecursors  

NASA Astrophysics Data System (ADS)

The use of electrochemically deposited macroprecursors for tethering polymers onto conducting surfaces is presented. Specifically, anodic electropolymerization was used as a tool to electrodeposit the precursors on electrodes that mediated the grafting of polymers onto surfaces. With this approach, patterning of surface-grafted polymers was also made possible through selective electrodeposition of the conjugated polymer network of the macroprecursors. This approach was used to fabricate protein and cell-resistant poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMEMA) brushes on Au surfaces. A chain transfer agent (CTA) was electrodeposited on the Au surface that served as the macroprecursor for the subsequent surface-initiated reversible addition-fragmentation chain transfer (SI-RAFT) polymerization of poly(ethylene glycol) methyl ether methacrylate (PEGMEMA). X-ray photoelectron spectroscopy (XPS) results showed the stability of the electrogenerated CTA under anodic conditions while successful brush growth was confirmed by surface techniques including XPS, ellipsometry, atomic force microscopy (AFM), and contact angle measurements. The PPEGMEMA-coated substrate exhibited protein and cell-repellant properties comparable to other reported PEG-functionalized surfaces. The proposed approach also yielded polymer-patterned surfaces as discussed in Chapters 3 and 4. An electroactive photocrosslinker was employed to facilitate the dual mode patterning of polystyrene (PS) on the surface by either electropatterning or photopatteming route. An electrodeposited CTA was also utilized to selectively grow surface-grafted PS on conducting regions of the substrate. Subsequent backfilling of nonconducting areas with a silane atom transfer radical polymerization (ATRP) initiator directed the growth of poly-N-isopropylacrylamide (PNIPAM) that produced a patterned binary polymer system. The patterns were successfully characterized by AFM and IR-imaging. Surface-grafted poly(N-vinyl carbazole) (PVK) film on indium tin oxide (ITO) was fabricated using this technique. This surface was used as a hole transporting layer (HTL) for a photovoltaic device as a possible replacement for existing poly(3,4-ethylene dioxythiophene) : poly(styrene sulfonate) (PEDOT:PSS). Device testing showed a comparable performance between the tethered PVK HTL and PEDOT:PSS as HTLs.

Rellamas Tria, Maria Celeste

382

Synthesis and property of poly(trimethylolpropane triacrylate)\\/Al nanocomposite particle by in situ solution polymerization  

Microsoft Academic Search

In order to improve its dispersibility and preserve its activity, nano-aluminum was encapsulated with poly(trimethylolpropane triacrylate) (PTMPTA) by in situ solution polymerization. The affecting factors of the conversion of monomer (CM), percentage of grafting (PG) and grafting efficiency (GE) were systematically studied. It was found that nano-aluminum had been evenly encapsulated with a layer of PTMPTA through chemical bond. And

Hui Liu; Hongqi Ye

2008-01-01

383

HIGH WATER ABSORBENTS FROM LIGNOCELLULOSES. I. EFFECT OF REACTION VARIABLES ON THE WATER ABSORBENCY OF POLYMERIZED LIGNOCELLULOSES  

Microsoft Academic Search

Hydrogels of 350 water-absorbency (g H2O2\\/g sample) and 900 water-keeping capacity (mL H2O2\\/g sample) were prepared from local lignocellulosic wastes. The wastes used are rice straw, sugar-cane bagasse, and cotton stalks. These hydrogels were prepared via graft–polymerization reaction using some vinyl monomers, followed by alkali hydrolysis. The effects of grafting parameters (concentration of both initiator and monomer, temperature, and time),

HOUSSNI EL-SAIED; AHMED I. WALY; ALTAF H. BASTA

2000-01-01

384

Thermal Degradation Behavior of Polystyrene\\/Magadiite Nanocomposites Prepared by Surface-initiated Nitroxide-Mediated Radical Polymerization  

Microsoft Academic Search

Exfoliated polystyrene (PS)\\/magadiite nanocomposites with a high suppression effect on thermal degradation were successfully prepared by in situ nitroxide-mediated radical polymerization of styrene monomer from the magadiite interlayer surface. Surface-initiated polymerization of styrene was conducted from the radical initiators immobilized on magadiite at 398 K. The number-average molecular weight (Mn) of the grafting PS increased with monomer conversion keeping a

Hideaki Yukutake; Motoyasu Kobayashi; Hideyuki Otsuka; Atsushi Takahara

2009-01-01

385

Durability of Polymeric Glazing and Absorber Materials  

SciTech Connect

The Solar Heating and Lighting Program has set the goal of reducing the cost of solar water heating systems by at least 50%. An attractive approach to such large cost reduction is to replace glass and metal parts with less-expensive, lighter-weight, more-integrated polymeric components. The key challenge with polymers is to maintain performance and assure requisite durability for extended lifetimes. The objective of this task is to quantify lifetimes through measurement of the optical and mechanical stability of candidate polymeric glazing and absorber materials. Polycarbonate sheet glazings, as proposed by two industry partners, have been tested for resistance to UV radiation with three complementary methods. Incorporation of a specific 2-mil thick UV-absorbing screening layer results in glazing lifetimes of at least 15 years; improved screens promise even longer lifetimes. Proposed absorber materials were tested for creep and embrittlement under high temperature, and appear adequate for planned ICS absorbers.

Jorgensen, G.; Terwilliger, K.; Bingham, C.; Milbourne, M.

2005-01-01

386

Radiation Induced Polymerization of Cyclophosphazene Trimers.  

National Technical Information Service (NTIS)

Hexachlorophosphazene was irradiated in bulk and in solution after various methods of purification. When rigorously dried and purified good yields of polymer were obtained. Poor reproducibility was found in the bulk but reasonably good results were obtain...

V. T. Stannett

1989-01-01

387

Study on the Mechanical and Thermal Properties of Jute-Reinforced Methyl Acrylate Grafted PET Composites  

Microsoft Academic Search

Polyethylene terephthalate (PET) granules were grafted with methyl acrylate (MA) from the solution containing 10% MA in methanol (86%) solvent and photo initiator (4%) for 10 min and then cured under UV radiation. MA-grafted PET films were prepared at 260°C and 5 ton pressure using heat press. Jute fabric-reinforced, MA-grafted, PET-based composites (25% fiber by weight) were fabricated by compression molding. Mechanical,

Ruhul A. Khan; Mubarak A. Khan; Haydar U. Zaman; Nazia Noor; Tanzina Huq; Avik Khan; Kamol Dey; Bapi Sarker; Suvasree Saha; M. Mushfequr Rahman; M. Saha; M. A. Gafur

2010-01-01

388

Entropic forces generated by grafted semiflexible polymers  

NASA Astrophysics Data System (ADS)

The entropic force exerted by the Brownian fluctuations of a grafted semiflexible polymer upon a rigid smooth wall are calculated both analytically and by Monte Carlo simulations. Such forces are thought to play an important role for several cellular phenomena, in particular, the physics of actin-polymerization-driven cell motility and movement of bacteria like Listeria. In the stiff limit, where the persistence length of the polymer is larger than its contour length, we find that the entropic force shows scaling behavior. We identify the characteristic length scales and the explicit form of the scaling functions. In certain asymptotic regimes, we give simple analytical expressions which describe the full results to a very high numerical accuracy. Depending on the constraints imposed on the transverse fluctuations of the filament, there are characteristic differences in the functional form of the entropic forces. In a two-dimensional geometry, the entropic force exhibits a marked peak.

Gholami, Azam; Wilhelm, Jan; Frey, Erwin

2006-10-01

389

Insitu grafting silica nanoparticles reinforced nanocomposite hydrogels.  

PubMed

Highly flexible nanocomposite hydrogels were prepared by using silica nanoparticles (SNPs) as fillers and multi-functional cross-links to graft hydrophilic poly(acrylic acid) (PAA) by free radical polymerization from an aqueous solution. The SNPs were collected by neighboring polymer chains and dispersed uniformly within a PAA matrix. The mechanical properties of the nanocomposite hydrogels were tailored by the concentration of SNPs according to the percolation model. It was proposed that covalent bonds of adsorbed chains on the filler surface resulted in the formation of a shell of an immobilized glassy layer and trapped entanglements, where the glassy polymer layer greatly enhanced the elastic modulus and the release of trapped entanglements at deformation contributed to the viscoelastic properties. PMID:24089085

Yang, Jun; Han, Chun-Rui; Duan, Jiu-Fang; Xu, Feng; Sun, Run-Cang

2013-10-03

390

Alveolar bone grafting  

PubMed Central

In patients with cleft lip and palate, bone grafting in the mixed dentition in the residual alveolar cleft has become a well-established procedure. The main advantages can be summarised as follows: stabilisation of the maxillary arch; facilitation of eruption of the canine and sometimes facilitation of the lateral incisor eruption; providing bony support to the teeth adjacent to the cleft; raising the alar base of the nose; facilitation of closure of an oro-nasal fistula; making it possible to insert a titanium fixture in the grafted site and to obtain favourable periodontal conditions of the teeth within and adjacent to the cleft. The timing of the ABG surgery take into consideration not only eruption of the canine but also that of the lateral incisor, if present. The best time for bone grafting surgery is when a thin shell of bone still covers the soon erupting lateral incisor or canine tooth close to the cleft.

Lilja, Jan

2009-01-01

391

[Molecular/polymeric magnetism  

SciTech Connect

New materials were synthesized to test the generality of magnetism in molecular/polymeric systems. The first room temperature molecular based magnet V(TCNE)[sub x][center dot]y(solvent) (1) is disclosed. The ferromagnetic and related transitions were studied in decamethylferrocenium tetracyanoethanide (TCNE), (1), and related materials. Our and others' models were tested for ferromagnetic and antiferromagnetic exchange between local sites; models for control of [Tc] were also tested.

Not Available

1993-01-01

392

Surface polymerization agents  

SciTech Connect

This is the final report of a 1-year, Laboratory-Directed R&D project at LANL. A joint technical demonstration was proposed between US Army Missile Command (Redstone Arsenal) and LANL. Objective was to demonstrate that an unmanned vehicle or missile could be used as a platform to deliver a surface polymerization agent in such a manner as to obstruct the filters of an air-breathing mechanism, resulting in operational failure.

Taylor, C.; Wilkerson, C.

1996-12-01

393

[Polymeric sorbents for hemoperfusion].  

PubMed

Applications of various sorbents and ion-exchange resins to hemoperfusion are reviewed. With respect to the type of processes accompanying removal of toxines from blood, the fillings of hemoperfusion columns are classified into the group of: sorbents, iono-sorbents and ion-exchangers, immunoadsorbents. Possibilities of improving hemocompatibility of polymeric materials used in hemoperfusion columns by a sorptive or covalent covering their surfaces with natural materials-heparin and/or albumin are discussed. PMID:2682576

Trochimczuk, A; Kolarz, B N

1989-01-01

394

Synthesis of well-defined, brush-type, amphiphilic [poly(styrene-co-2-hydroxyethyl methacrylate)-graft-poly(?-caprolactone)]-b-poly(ethylene oxide)-b-[poly(styrene-co-2-hydroxyethyl methacrylate)-graft-poly(?-caprolactone)] and its aggregation behavior inaqueous media  

Microsoft Academic Search

Brush-type, amphiphilic (poly(styrene-co-2-hydroxyethyl methacrylate)- graft-poly(e-caprolactone))-b-poly(ethylene oxide)-b-(poly(styrene-co-2-hydroxyethyl me- thacrylate)-graft-poly(e-caprolactone)) was successfully synthesized via consecutive ring- opening anionic polymerization, reversible addition-fragmentation chain transfer (RAFT) polymerization, and coordination-insertion ring-opening polymerization (ROP). Two poly (ethylene oxide) macro-RAFT agents with two 3-benzylsulfanylthiocarbonylsufanyl pro- pionic acid end groups were prepared by the reaction of Poly(ethylene oxide) with hydroxyl group at two ends (HO-PEO-OH) with 3-benzylsulfanylthiocarbonylsufanyl propionic

Xuewei Xu; Zhongfan Jia; Ruiming Sun; Junlian Huang

2006-01-01

395

On the mechanisms of radiation-induced curing of epoxy-fiber composites  

NASA Astrophysics Data System (ADS)

Depending on the monomer molecular structure, the mechanisms of radiation-induced polymerization proceed via either C-centered radical mechanisms or cationic polymerization. While polymerization via C-centered radicals can be impeded by the presence of oxygen and high dose-rate, polymerization through cationic polymerization is inhibited even by the presence of trace amounts of water. Synergy by the combination of radiation and thermal curing can help to achieve various desired properties of polymer-fiber composite materials.

Al-Sheikhly, Mohamad; McLaughlin, William L.

1996-08-01

396

Miscible blends of poly(butyl methacrylate) densely grafted on fumed silica with poly(vinyl chloride)  

Microsoft Academic Search

Poly(butyl methacrylate) (PBMA) densely grafted on a fumed silica particle consisting of primary particles with an average diameter of 14nm, has been synthesized by surface-initiated atom transfer radical polymerization (SI-ATRP). In these syntheses, a newly designed initiator, p-(bromomethyl)benzyl 2-bromoisobutylate was used for the immobilization of the initiator moiety on the silica particle to give the densely grafted PBMA. Thus synthesized

Kenichi Hayashida; Hiromitsu Tanaka; Osamu Watanabe

2009-01-01

397

Post-irradiation grafting of tetrafluoroethylene at low temperatures. [Gamma rays  

SciTech Connect

Low-temperature postirradiation grafting of tetrafluoroethylene (TFE) to polyolefines and silicone elastomers was the subject of study. After preliminary dissolution of TFE in the polymer at 273/sup 0/K the system was slowly cooled to 77/sup 0/K. In this process a certain part of TFE in polyolefines (ethylene-propylene copolymer and polypropylene) is retained by the vitreous polymer matrix. When slowly heated after radiolysis at 77/sup 0/K this system shows graft polymerization of dissolved TFE after T/sub g/. The graft copolymer is soluble and its IR spectra contain absorption bands characteristic of polytetrafluoroethylene. In polydimethylsiloxane rubber (SKT) the dissolved TFE when frozen to 77/sup 0/K remains sorbed between the SKT crystallites rather than in a separate phase. When those radiolyzed samples are heated the graft-polymerization occurs primarily over the temperature range between the TFE and SKT melting points. The technique provides for 100 to 150% grafting of TFE. This method also permits grafting to silicone rubbers and to several other polymers and elastomers.

Barkalov, I.M.; Kiryukhin, D.P.; Muydinov, M.R.

1981-09-01

398

Effective force between colloidal particles with end-grafted long polymer chains dissolved in a high-molecular weight solvent  

Microsoft Academic Search

We aim at the determination of the effective force between colloidal particles clothed each by f end-grafted long polymer chains of polymerization degree N, which are immersed in a melt of short chains of polymerization degree P

M Himmi; M Benhamou; A Bettachy

2004-01-01

399

Polymeric salt bridges for conducting electric current in microfluidic devices  

SciTech Connect

A "cast-in-place" monolithic microporous polymer salt bridge for conducting electrical current in microfluidic devices, and methods for manufacture thereof is disclosed. Polymeric salt bridges are formed in place in capillaries or microchannels. Formulations are prepared with monomer, suitable cross-linkers, solvent, and a thermal or radiation responsive initiator. The formulation is placed in a desired location and then suitable radiation such as UV light is used to polymerize the salt bridge within a desired structural location. Embodiments are provided wherein the polymeric salt bridges have sufficient porosity to allow ionic migration without bulk flow of solvents therethrough. The salt bridges form barriers that seal against fluid pressures in excess of 5000 pounds per square inch. The salt bridges can be formulated for carriage of suitable amperage at a desired voltage, and thus microfluidic devices using such salt bridges can be specifically constructed to meet selected analytical requirements.

Shepodd, Timothy J. (Livermore, CA); Tichenor, Mark S. (San Diego, CA); Artau, Alexander (Humacao, PR)

2009-11-17

400

Bone Grafts in Craniofacial Surgery  

PubMed Central

Reconstruction of cranial and maxillofacial defects is a challenging task. The standard reconstruction method has been bone grafting. In this review, we shall describe the biological principles of bone graft healing, as pertinent to craniofacial reconstruction. Different types and sources of bone grafts will be discussed, as well as new methods of bone defect reconstruction.

Elsalanty, Mohammed E.; Genecov, David G.

2009-01-01

401

Cystocele repair with interpositional grafting.  

PubMed

This article discusses a systematic approach to the repair of cystoceles using interposition grafting. Surgeons' opinions vary regarding which graft is most appropriate as there are several varieties for mesh interposition. High-grade cystocele repair using the porcine dermis interposition graft is successful and associated with few complications. Cystocele repair is typically low grade and does not require additional surgery. PMID:21353079

Leu, Patrick B; Scarpero, Harriette M; Dmochowski, Roger R

2011-02-01

402

Nucleation-controlled polymerization of nanoparticles into supramolecular structures.  

PubMed

Controlled assembly of inorganic nanoparticles (NPs) into structurally defined supramolecular polymers will create nanomaterials with new collective properties. However, supramolecular polymerization of isotropic NPs remains a challenge because of the lack of anisotropic interactions in these monomers to undergo directional associations for the cooperative growth of supramolecular chains. Herein we report self-assembly behavior of poly(l-glutamic acid)-grafted gold NPs in solution and describe how combined attractive and repulsive interactions influence the shape and size of the resulting supramolecular assemblies. The study shows that the chain growth of supramolecular polymers can be achieved from the NP monomers and the process occurs in two distinct stages, with a slow nucleation step followed by a faster chain propagation step. The resulting supramolecular structures depend on both the grafting density of the poly(l-glutamic acid) on the NPs and the size of the NPs. PMID:23697509

Wang, Jing; Xia, Hongwei; Zhang, Yanfeng; Lu, Hua; Kamat, Ranjan; Dobrynin, Andrey V; Cheng, Jianjun; Lin, Yao

2013-05-22

403

POLYMERIZATION OF MONOMERIC TO POLYMERIC VESICLES. CHARACTERIZATION AND APPLICATIONS  

Microsoft Academic Search

The first reports on the polymerization of monomeric vesicles to their polymerized counterparts [1–18] appeared in the literature in the early 1980s. The primary goal of this early work was to stabilize the relatively unstable monomeric vesicles in order to stimulate the function of biological membranes. Triggered by these at-tempts and the prospects for utilization of polymerized vesicles as energy

Constantinos N. Paleos

1990-01-01

404

Preparation and Characterization of Cotton Textile Graft Copolymers as Cation Exchanger  

NASA Astrophysics Data System (ADS)

Acrylic Acid (AA) was graft copolymerized with cotton cellulose in fabric form to prepare poly (AA)-cotton graft copolymer cation exchanger using Fe2+/BrO3- redox system in aqueous medium under a nitrogen atmosphere. The effect of Fe2+, BrO3- and monomer concentrations, pH as well as time and temperature of polymerization were studied by determining the grafting parameters gravimetrically, like Graft Yield (GY %) and Graft Reaction Efficiency (GRE %). On the other hand, the newly prepared poly (AA)-cotton graft copolymers were characterized for different heavy metals ions removal to determined their suitability as cation exchanger. On the basis of a detailed investigation of the above factors, the appropriate conditions for grafting were as follows: Fe2+, 0.005 mol L-1; BrO3-, 0.001 mol L-1; pH, 2; monomer, (50% based on weight of substrate); time, 90 min and temperature, 35°C. On the other hand, the potential value of the newly prepared poly (AA)-cotton graft copolymer to serve as cation exchanger was assessed through measurements of critical properties such as removal of different heavy metal ions from their solutions as well as durability.

Mostafa, Kh. M.

2005-03-01

405

Vascular graft infections.  

PubMed

Vascular procedures are rarely complicated by infection, but if prosthetic vascular graft infection (PVGI) occurs, morbidity and mortality are high. Several patient-related, surgery-related and postoperative risk factors are reported, but they are not well validated. PVGI is due to bacterial colonisation of the wound and the underlying prosthetic graft, generally as a result of direct contamination during the operative procedure, mainly from the patient's skin or adjacent bowel. There is no consensus on diagnostic criteria or on the best management of PVGI. On the basis of reported clinical studies and our own experience, we advocate a surgical approach combining repeated radical local debridement, with graft preservation whenever possible or partial excision of the infected graft, depending on its condition, plus simultaneous negative-pressure wound therapy (NPWT). In addition, antimicrobial therapy is recommended, but there is no consensus on which classes of agent are adequate for the treatment of PVGI and whether certain infections may be treated by means of NPWT alone. Since staphylococci and Gram-negative rods are likely to be isolated, empirical treatment might include a penicillinase-resistant beta-lactam or a glycopeptide, plus an aminoglycoside, the latter for Gram-negative coverage and synergistic treatment of Gram-positive cocci. Additionally, empirical treatment might include rifampicin since it penetrates well into biofilms. PMID:23348860

Hasse, Barbara; Husmann, Lars; Zinkernagel, Annelies; Weber, Rainer; Lachat, Mario; Mayer, Dieter

2013-01-24

406

Radiation Curing of Fabric Reinforced Elastomeric Composites.  

National Technical Information Service (NTIS)

Ionizing radiation from cobalt-6O gamma and electron beam sources are used to investigate methods to improve the abrasion resistance of polyurethane elastomers. Radiation curing of acrylated urethane oligomers and grafting acrylonitrile onto polyurethanes...

W. J. Chappas F. J. Chang J. Silverman

1997-01-01

407

SPACE ENVIRONMENTAL EFFECTS ON SEALS, GASKETS, ADHESIVES AND OTHER ELASTOMERIC AND POLYMERIC MATERIALS: AN ANNOTATED BIBLIOGRAPHY  

Microsoft Academic Search

Issued as an Addendum to the Space Materials Handbook. This ; bibliography contains 558 selected references on seals, gaskets, adhesives, ; sealants, and other elastomeric and polymeric materials under space conditions. ; Environmental conditions that will effect materials in space are exposure to ; high vacuum, service temperatures, and radiation. Radiation includes ultraviolet ; and high-energy radiation as appropriate to

H. M. comp

1961-01-01

408

Models for actin polymerization motors  

Microsoft Academic Search

Actin polymerization drives cell membrane protrusions and the propulsion of intracellular pathogens. The molecular mechanisms\\u000a driving actin polymerization are not yet fully understood. Various mathematical models have been proposed to explain how cells\\u000a convert chemical energy released upon actin polymerization into a pushing force on a surface. These models have attempted\\u000a to explain puzzling properties of actin-based motility, including persistent

Richard B. Dickinson

2009-01-01

409

Living olefin polymerization processes  

DOEpatents

Processes for the living polymerization of olefin monomers with terminal carbon-carbon double bonds are disclosed. The processes employ initiators that include a metal atom and a ligand having two group 15 atoms and a group 16 atom or three group 15 atoms. The ligand is bonded to the metal atom through two anionic or covalent bonds and a dative bond. The initiators are particularly stable under reaction conditions in the absence of olefin monomer. The processes provide polymers having low polydispersities, especially block copolymers having low polydispersities. It is an additional advantage of these processes that, during block copolymer synthesis, a relatively small amount of homopolymer is formed.

Schrock, Richard R. (Winchester, MA); Baumann, Robert (Cambridge, MA)

1999-01-01

410

Living olefin polymerization processes  

DOEpatents

Processes for the living polymerization of olefin monomers with terminal carbon-carbon double bonds are disclosed. The processes employ initiators that include a metal atom and a ligand having two group 15 atoms and a group 16 atom or three group 15 atoms. The ligand is bonded to the metal atom through two anionic or covalent bonds and a dative bond. The initiators are particularly stable under reaction conditions in the absence of olefin monomer. The processes provide polymers having low polydispersities, especially block copolymers having low polydispersities. It is an additional advantage of these processes that, during block copolymer synthesis, a relatively small amount of homopolymer is formed.

Schrock, R.R.; Baumann, R.

1999-03-30

411

Antimicrobial polymeric surfaces  

US Patent & Trademark Office Database

Bactericidal compositions are disclosed that comprise a polymeric compound immobilized on a material. Medical devices are also disclosed which comprise such a bactericidal composition. Methods are disclosed for covalently derivatizing the surfaces of common materials with an antibacterial polycation, e.g., poly(vinyl-N-pyridinium bromide); the first step of the methods involves coating the surface with a nanolayer of silica. Various commercial synthetic polymers derivatized in this manner are bactericidal, i.e., they kill on contact up to 99% of deposited Gram-positive and Gram-negative bacteria, whether deposited through air or water.

Tiller; Joerg C. (Cambridge, MA); Liao; Chun-Jen (Taipei, TW); Lewis; Kim (Newton, MA); Klibanov; Alexander M. (Newton, MA)

2006-12-19

412

Microwave initiated synthesis of polyacrylamide grafted Psyllium and its application as a flocculant.  

PubMed

This paper reports a novel microwave initiated method for synthesis of polyacrylamide grafted Psyllium (Psy-g-PAM). Psyllium was modified through grafting of polyacrylamide (PAM) chains on it using microwave radiations only, in absence of any other free radical initiator. The grafting was confirmed by intrinsic viscosity study and characterization techniques like FTIR spectroscopy, elemental analysis (C, H, N, O and S) and SEM morphology study. Further, the flocculation efficacy of the synthesized graft copolymers was studied in kaolin and coal fine suspension through standard 'Jar test' procedure. PMID:22210527

Sen, Gautam; Mishra, Sumit; Rani, G Usha; Rani, Priti; Prasad, Rajesh

2011-12-23

413

Grafting parameters in the copolymerization by irradiation of N,N- dimethylacrylamide (DMAA) onto Aflon Films.  

National Technical Information Service (NTIS)

The radiation-induced grafting has been studied to modify chemical structures and physical properties of polymers (Allen et al, 1955). In the synthesis of biocompatible membranes is specially useful to impart hydrophilic property to the originally hydroph...

A. A. A. Queiroz O. Z. Higa

1990-01-01

414

CO2 - pulsed laser induced surface grafting of acrylamide onto ethylene - propylene rubber (EPR). II  

NASA Astrophysics Data System (ADS)

A line tunable CO2 - pulsed laser (TEA CO2 laser Lumonics - 103-2) which operates at 9.1 - 10.6?m has been employed to induce grafting of acrylamide(AAm) onto the surface of EPR in the presence of Benzophenone (BP) and azobisisobutyronitrile(AZBN) as sensitizer. Characterization has been carried out using ATR-IR(FT), EDXA , and SEM. Grafting of AAm occures providing the system is excited by pulses with the wavelength corresponding to the absorption maxima of the sensitizer. Fractal type of morphology is formed by the grafted polyAAm. Both graft yield and size of fractals are dependent upon the exciting wavelength and laser pulsing frequency. Results reveal that co-polymerization of AAm occures by vibrational excitation of AAm or the used photosensitizer via multiphoton absorption mechanism.

Mirzadeh, H.; Katbab, A. A.; Burford, R. P.

1993-07-01

415

Bioinert membranes prepared from amphiphilic poly(vinyl chloride)-g-poly(oxyethylene methacrylate) graft copolymers.  

PubMed

Poly(vinyl chloride) (PVC) membrane was hydrophilically modified by grafting with poly(oxyethylene methacrylate) (POEM) using atom transfer radical polymerization (ATRP). The successful grafting of PVC main chain by POEM was characterized by Fourier transform infrared spectroscopy (FT-IR). The molecular weight and hydrophilicity of membranes increased with the amount of POEM grafting, as characterized by gel permeation chromatography (GPC) and contact angle measurement, respectively. Transmission electron microscope (TEM) and small angle X-ray scattering (SAXS) analysis revealed the microphase-separated structure of PVC-g-POEM and the domain spacing increased from 59.3 to 86.1 nm with increasing grafting degree. Scanning electron microscopy (SEM) was used for the direct visualization of the mouse embryonic fibroblast (MEF) cell and bacteria adhesion on the membrane surface. Protein adsorption and eukaryotic and prokaryotic cell adhesion tests showed that the bioinert properties of membranes were significantly increased with POEM content. PMID:23827621

Patel, Rajkumar; Patel, Madhumita; Ahn, Sung Hoon; Sung, Yong Kiel; Lee, Hyung-Keun; Kim, Jong Hak; Sung, Jung-Suk

2013-01-07

416

Preparation and characterization of poly(isobutyl methacrylate) microbeads with grafted amidoxime groups  

NASA Astrophysics Data System (ADS)

Poly(isobutyl methacrylate) (PiBMA) microspheres with a 800- to 1500-?m diameter range synthesized by suspension polymerization technique were used as the trunk polymer in the preparation of a highly efficient new adsorbent. Glycidyl methacrylate (GMA) was grafted onto the trunk polymer by pre-irradiation grafting technique. Grafting conditions were optimized, and GMA grafted PiBMA beads were modified with iminodiacetonitrile (IDAN) in ethanol at 80 °C. The nitrile groups were then amidoximated by using 6% (m/v) hydroxylamine hydrochloride in methanol solution. The IDAN modification and the conversion of the nitrile groups to amidoxime were followed by FT-IR spectroscopy. The surface morphology and thermal behavior of the PiBMA and its modificated forms were also characterized by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques further confirming modification and amidoximation.

Çaykara, Tuncer; Alaslan, ?erife ?irin; Gürü, Metin; Bodugöz, Hatice; Güven, Olgun

2007-10-01

417

Preparation of magnetic polymeric composite nanoparticles by seeded emulsion polymerization  

Microsoft Academic Search

Seeded emulsion polymerization was used to prepare magnetic polymeric composite nanoparticles (MPCNPs) with the aim to successfully encapsulate magnetite particles and to improve particle size distribution (PSD). Microscopical morphology and number-average diameter of hydrophilic magnetite particles (HMPs), magnetic seed latex nanoparticles (MSLNPs) and MPCNPs were observed and analyzed by transmission electron microscope (TEM). Weight-average diameter and PSD of MSLNPs and

Shulai Lu; Rongjun Qu; Jacqueline Forcada

2009-01-01

418

Temperature-induced chiral nematic phase changes of suspensions of poly( N , N -dimethylaminoethyl methacrylate)-grafted cellulose nanocrystals  

Microsoft Academic Search

Temperature-induced copolymers of poly(N,N-dimethylaminoethyl methacrylate)-grafted cellulose nanocrystals (PDMAEMA-grafted CNC) were synthesized by surface-initiated\\u000a atom transfer radical polymerization (ATRP). The graft copolymers were characterized by thermogravimetric analysis (TGA),\\u000a Fourier-transform infrared spectroscopy (FT-IR), and gel permeation chromatography (GPC). The size of the original CNC was\\u000a 10–40 nm in width and 100–400 nm in length, as characterized by atomic force microscopy (AFM). The liquid-crystalline properties

Jie Yi; Qunxing Xu; Xuefei Zhang; Hailiang Zhang

2009-01-01

419

Polymeric membranes for hybrid liver support devices: The effect of membrane surface wettability on hepatocyte viability and functions  

Microsoft Academic Search

Extracorporeal therapies based on membrane hybrid liver support devices using primary hepatocytes are an interesting approach to the treatment of acute hepatic failure. In such devices, semipermeable polymeric membranes are effectively used as immunoselective barriers between a patient's blood and the xenocytes in order to prevent the immune rejection of the graft. The membranes may act also as the substratum

G. Catapano; M. C. Di Lorenzo; C. Della Volpe; L. De Bartolo; C. Migliaresi

1996-01-01

420

An ultra-sensitive microfluidic immunoassay using living radical polymerization and porous polymer monoliths.  

SciTech Connect

We present a platform that combines patterned photopolymerized polymer monoliths with living radical polymerization (LRP) to develop a low cost microfluidic based immunoassay capable of sensitive (low to sub pM) and rapid (<30 minute) detection of protein in 100 {micro}L sample. The introduction of LRP functionality to the porous monolith allows one step grafting of functionalized affinity probes from the monolith surface while the composition of the hydrophilic graft chain reduces non-specific interactions and helps to significantly improve the limit of detection.

Abhyankar, Vinay V.; Singh, Anup K.; Hatch, Anson V.

2010-07-01

421

Versatile functionalization of Fe3O4 nanoparticles via RAFT polymerization and click chemistry  

NASA Astrophysics Data System (ADS)

Azide-functionalized chain transfer agent (CTA) was synthesized and subsequently employed to mediate the reversible addition fragmentation transfer (RAFT) polymerization of poly(ethylene glycol) monomethacrylate (PEGMA) on the alkyne-functionalized Fe3O4 nanoparticles surface together with click chemistry. In a single pot procedure, azide-functionalized CTA, alkyne-functionalized Fe3O4 and PEGMA were combined to produce the desired product. Fourier transformed infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA) results showed that PEGMA chains were grafted to Fe3O4 nanoparticles using RAFT polymerization and click chemistry.

Zhou, Yang; Wang, Shixing; Xie, Keqiang; Dai, Yongnian; Ma, Wenhui

2011-10-01

422

Grafted megaporous materials as ion-exchangers for bioproduct adsorption.  

PubMed

Megaporous chromatographic materials were manufactured by a three-step procedure, including backbone synthesis, chemical grafting, and introduction of ion-exchange functionality. The backbone of the adsorbent cylindrical bodies was prepared by polymerization of methacrylic acid and poly(ethylene glycol) diacrylate at sub-zero temperatures. Grafting was performed employing glycidyl methacrylate and a chemical initiator, cerium ammonium nitrate. The degree of grafting was adjusted by modifying the concentration of the initiator in the reaction mixture to a range of values (23, 39, 62, 89, and 105%). Further, the pendant epoxy-groups generated by the previous step were reacted to cation- and anion-exchanging moieties utilizing known chemical routes. Infrared spectroscopy studies confirmed the incorporation of epoxy and ion-exchanger groups to the backbone material. Optimized materials were tested for chromatography applications with model proteins; the dynamic binding capacity, as recorded at 10% breakthrough and 2.0 × 10(-4) m/s superficial velocity, were 350 and 58 mg/g for the cation-exchanger and the anion-exchanger material, respectively. These results may indicate that long tentacle-type polymer brushes were formed during grafting therefore increasing the ability of the megaporous body to efficiently capture macromolecules. PMID:23401432

Bibi, Noor Shad; Fernández-Lahore, Marcelo

2013-03-07

423

Periorbital fat grafting.  

PubMed

Periorbital aging is a multifactorial process involving volume loss (bone and soft tissue), tissue decent, and cutaneous degenerative changes. Traditional approaches to surgery on this area of the face have been subtractive in nature, focusing on excision of skin, muscle, and fat. This has frequently led to a gaunt or hollowed postoperative appearance. Contemporary aesthetic eyelid and periorbital rejuvenation has undergone a paradigm shift from an excisionally based surgical approach to one that prioritizes volume preservation and/or augmentation. The development of fat grafting to the eyelids and periorbita has given the eyelid surgeon a viable surgical alternative to prevent postoperative volume depletion, maintain the smooth transition of the lower eyelid to the cheek, and aid in restoring the youthful appearance desired after surgery. This article will focus of periorbital fat grafting and touch upon fat preservation techniques as primary restorative procedures or as surgical adjuncts. PMID:23426752

Massry, Guy G; Azizzadeh, Babak

2013-02-20

424

Biocompatible Initiators for Lactide Polymerization  

Microsoft Academic Search

The review summarizes recent developments in the preparation and use of new initiators for the ring opening polymerization of lactide. The review compares different classes of initiator including metal complexes, classed according to their group in the periodic table, and carbon?based initiators\\/organocatalysts. Emphasis is placed on the polymerization kinetics and the control exhibited by the different types of initiators. Where

Rachel H. Platel; Linda M. Hodgson; Charlotte K. Williams

2008-01-01

425

Two Photon Polymerization of Ormosils  

Microsoft Academic Search

In this work, 3D structures of hybrid polymers-ORMOSILS (organically modified silicates) were produced via Two Photon Polymerization (2PP) of hybrid methacrylates based on silane derivates. Synthetic routes have been used to obtain series of hybrid monomers, their structure and purity being checked by NMR Spectroscopy and Fourier Transform Infrared Spectroscopy. Two photon polymerization method (a relatively new technology which allows

A. Matei; M. Zamfirescu; F. Jipa; C. Luculescu; M. Dinescu; E. C. Buruiana; T. Buruiana; L. E. Sima; S. M. Petrescu

2010-01-01

426

Siloxane-grafted membranes  

DOEpatents

Composite cellulosic semipermeable membranes are disclosed which are the covalently bonded reaction product of an asymmetric cellulosic semipermeable membrane and a polysiloxane containing reactive functional group. The two reactants chemically bond by ether, ester, amide or acrylate linkages to form a siloxane-grafted cellulosic membrane having superior selectivity and flux stability. Selectivity may be enhanced by wetting the surface with a swelling agent such as water.

Friesen, D.T.; Obligin, A.S.

1989-10-31

427

Synthesis and applications of poly(2-hydroxyethylmethacrylate) grafted agar: A microwave based approach.  

PubMed

Synthesis of graft copolymers under the influence of microwave radiation alone is a rapid, efficient, clean, cheap, convenient, energy-saving and green method. Grafting of poly(2-hydroxyethylmethacrylate) on agar backbone was carried out under the influence of microwave radiation. The synthesis is optimized in terms of percentage grafting and intrinsic viscosity, by varying the microwave irradiation time and monomer (2-hydroxyethylmethacrylate) concentration. The synthesized graft copolymers have been characterized by intrinsic viscosity measurement, FTIR spectroscopy, UV-spectroscopy, elemental analysis (C, H, N, & S), thermal studies and scanning electron microscopy (SEM). Flocculation efficacy of the synthesized graft copolymers was studied in 0.25% kaolin and 1% coal fine suspension, through 'jar test' procedure. Further, flocculation efficacy of the best grade, coagulant (alum) and agar were studied for possible application in remediation of metals from river water. PMID:23850679

Rani, G Usha; Mishra, Sumit; Pathak, Gopal; Jha, Usha; Sen, Gautam

2013-07-10

428

Understanding the grafting of telechelic polymers on a solid substrate to form loops  

SciTech Connect

Recent experimental and theoretical studies have demonstrated that relative to singly tethered chains, the presence of polymer loops at interfaces significantly improves interfacial properties such as adhesion, friction, and wettability. In the present study, a simple system was studied to examine the formation of polymeric loops on a solid surface, where the grafting of carboxylic acid terminated telechelic polystyrene from the melt to an epoxy functionalized silicon is chosen. The impact of telechelic molecular weight, grafting temperature, and surface functionality on the telechelic attachment process is studied. It was found that grafting of the telechelic to the surface at both ends to form loops is the primary product of this grafting process. Moreover, examination of the kinetics of the grafting process indicates that it is reaction controlled. Fluorescence tagging of the dangling ends of singly bound chains provides a mechanism to monitor their time evolution during grafting, and these results indicate that the grafting process is accurately described by recent Monte Carlo simulation work. The results also provide a method to control the extent of loop formation at interfaces and therefore provide an opportunity to further understand the role of the loops in the interfacial properties in multicomponent polymer systems.

Huang, Zhenyu [University of Tennessee, Knoxville (UTK); Ji, Haining [ORNL; Mays, Jimmy [ORNL; Dadmun, Mark D [ORNL

2008-01-01

429

Investigating adsorption of synthetic nanoparticles and biological species using surface-grafted molecular and macromolecular gradient assemblies  

Microsoft Academic Search

We utilize novel surface-grafted molecular and macromolecular gradient assemblies to investigate: (1) dispersion of nanoparticles in organic matrices tethered to a substrate, and (2) adsorption of proteins and adhesion of cells to synthetic polymeric surfaces. First, we demonstrate control over the two-dimensional assemblies of nanoparticles bound to a flat substrate by utilizing a concentration gradient template formed via vapor transport

Rajendra R. Bhat

2005-01-01

430

Infected grafts of incisional hernioplasties  

Microsoft Academic Search

Summary  Prosthetic grafts are used often enough for incisional hernioplasty to familiarize surgeons with the management of some complications\\u000a that are bound to occasionally occur despite correct medical decisions and excellent surgical technique. This paper discusses\\u000a five cases of infection in grafted incisional hernioplasties. Two are examples of the possibility that exposed and infected\\u000a grafts can be saved in spite of

A. I. Gilbert; M. F. Graham

1997-01-01

431

Polymer brushes on carbon nanotubes by thiol-lactam initiated radical polymerization of 2-hydroxyethyl methacrylate.  

PubMed

Water-soluble polymer brushes with multi-walled carbon nanotubes (MWNTs) as backbones were synthesized by grafting 2-hydroxyethyl methacrylate (HEMA) from surface functionalized MWNTs via in situ surface thiol-lactam initiated radical polymerization. MWNTs were functionalized with 2-mercaptoethanol and used as initiators in the polymerization of HEMA in the presence of butyrolactam. FT-IR, XPS, 1H NMR, GPC and TGA were used to determine chemical structure and the grafted polymer quantities of the resulting product. The covalent bonding of PHEMA to the MWNTs dramatically improved the water dispersibility of MWNTs. The average thicknesses of the polymer brushes in the functionalized MWNTs were detected with electron microscopy (SEM and TEM) and images indicated that the nanotubes were coated with polymer layer. PMID:22524067

Rashid, Md Harun-Or; Lee, Won-Ki; Hong, Seong-Soo; Park, Jong Myung; Kim, Hyun Gyu; Lim, Kwon Taek

2012-01-01

432

Corrosion protection of iron surface modified by poly(methyl methacrylate) using surface-initiated atom transfer radical polymerization (SI-ATRP)  

Microsoft Academic Search

A new N-heterocyclic initiator N-[2-(8-heptadecenyl)-4,5-dihydro-1H-imidazole-1-ethyl]-2-bromoisobutyramide was synthesized and immobilized on the surface of iron. Methyl methacrylate was grafted\\u000a from iron substrates via surface-initiated atom transfer radical polymerization (ATRP). The first-order kinetics of poly(methyl\\u000a methacrylate) (PMMA) grafting from iron revealed the control of ATRP throughout the reaction, and the polymerization reached\\u000a a high conversion producing polymers with good control of molecular

Gang Lu; Yi-Min Li; Chun-Hua Lu; Zhong-Zi Xu

2010-01-01

433

Surface modification of biomaterials by photochemical immobilization and photograft polymerization to improve hemocompatibility  

Microsoft Academic Search

Thrombus formation and blood coagulation are serious problems associated with blood contacting products, such as catheters,\\u000a vascular grafts, artificial hearts, and heart valves. Recent progresses and strategies to improve the hemocompatibility of\\u000a biomaterials by surface modification using photochemical immobilization and photograft polymerization are reviewed in this\\u000a paper. Three approaches to modify biomaterial surfaces for improving the hemocompatibility, i.e., bioinert surfaces,

Yakai Feng; Haiyang Zhao; Li Zhang; Jintang Guo

2010-01-01

434

Thermal stabilities of polystyrene\\/silica hybrid nanocomposites via microwave-assisted in situ polymerization  

Microsoft Academic Search

Serials of polystyrene\\/silica nanocomposites (PS\\/SNs) with different content of inorganic nanofillers were successfully prepared by the in situ bulk radical copolymerization of styrene with a macromonomers, methacryloxypropyl silica nanoparticles (MPSNs) under microwave irradiation. A percentage of grafting (PG%) of 33.14% could be achieved under the optimized polymerizing condition with a conversion of styrene (C%) of 98.92%. The thermogravimetric analysis (TGA)

Peng Liu; Zhixing Su

2005-01-01

435

Directly growing ionic polymers on multi-walled carbon nanotubes via surface RAFT polymerization  

Microsoft Academic Search

RAFT agents were attached to multi-walled carbon nanotubes (MWNTs); subsequently, different kinds of aqueous soluble ionic polymer chains, such as cationic polymer (poly(2-(dimethylamino) ethylmethacrylate)), anionic polymer (poly(acrylic acid)) and zwitterionic polymer (poly{3-[N-(3- methacrylamidopropyl)-N,N-dimethyl] ammoniopropane sulfonate}) were easily to grafted onto the surface of MWNTs directly by surface reversible addition-fragmentation chain transfer (RAFT) polymerization. The produced poly{3-[N-(3-methacrylamidopropyl)-N,N-dimethyl] ammoniopropane sulfonate} functionalized MWNTs,

Ye-Zi You; Chun-Yan Hong; Cai-Yuan Pan

2006-01-01

436

Synthesis and antitumor activity of doxorubicin conjugated stearic acid- g-chitosan oligosaccharide polymeric micelles  

Microsoft Academic Search

Doxorubicin conjugated stearic acid-g-chitosan oligosaccharide polymeric micelles (DOX–CSO–SA) was synthesized via cis-aconityl bond between the anticancer drug doxorubicin (DOX) and stearic acid grafted chitosan oligosaccharide (CSO–SA) in this paper. The CSO–SA micelles had been demonstrated faster internalization ability into tumor cells. Here, the CSO–SA with 6.47% amino substituted degree (SD%) was used to synthesize DOX–CSO–SA. The critical micelle concentration (CMC)

Fu-Qiang Hu; Li-Na Liu; Yong-Zhong Du; Hong Yuan

2009-01-01

437

Synthesis of water-soluble carbon nanotubes via surface initiated redox polymerization and their tribological properties as water-based lubricant additive  

Microsoft Academic Search

Polyacrylamide (PAM)-grafted multi-walled carbon nanotubes (MWCNTs-g-PAM) which are dispersable in water were prepared by the surface initiated redox polymerization of acrylamide using ceric ammonium nitrate (CAN) as initiator. They are soluble in polar solvents such as water, tetrahydrofuran and acetone. The chemical structure of the resulting product and the quantities of grafted polymer were determined by FT-IR, TGA. TEM, and

Xiaowei Pei; Litian Hu; Weimin Liu; Jingcheng Hao

2008-01-01

438

Functionalized cotton via surface-initiated atom transfer radical polymerization for enhanced sorption of Cu(II) and Pb(II)  

Microsoft Academic Search

The surface-initiated atom transfer radical polymerization (ATRP) was used to successfully prepare the aminated cotton and polyacrylic acid sodium (P(AA-Na))-grafted cotton for the efficient removal of Cu(II) and Pb(II) from aqueous solution in this study. The modified cotton surfaces were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). The grafted long polymers with

Y. Q. Zheng; Shubo Deng; Li Niu; F. J. Xu; M. Y. Chai; Gang Yu

2011-01-01

439

In situ polymerization and in situ compatibilization of polymer blends of poly(2,6-dimethyl-1,4-phenylene oxide) and polyamide 6  

Microsoft Academic Search

A novel approach of in situ polymerization and in situ compatibilization was adopted to prepare compatibilized PPO\\/PA6 blends. An anionic ring-opening polymerization of ?-caprolactam was proceeded in the presence of PPO, whose chain bore p-methoxyphenyl-propionate (MPAA), acting as macroactivator to initiate PA6 chain growth from the PPO chains and to form a graft copolymer of PPO and PA6 and pure

Yali Ji; Jinghong Ma; Borun Liang

2005-01-01

440

Preparation of magnetic polymeric particles via inverse microemulsion polymerization process  

NASA Astrophysics Data System (ADS)

Hydrophilic submicron magnetic polymeric particles were prepared using inverse microemulsion polymerization process. Firstly, the magnetic properties of iron oxide nanoparticles elaborated were examined using X-ray diffraction and magnetization analysis of the chemical structure and the magnetic properties, respectively. The results obtained using stoichiometric precipitation of FeCl2 and FeCl3 revealed the magnetite iron oxide properties. Secondly, various magnetic polymeric latexes were prepared by investigating the effect of surfactant (AOT) concentration, the amount of cross-linker (MBA), the initiator nature and the microemulsion elaboration methodology. The colloidal characterization of the final magnetic polymeric latexes revealed to be submicronic in size, spherical in morphology, containing 5-23wt% iron oxide and superparamagnetic in character.

Deng, Y.; Wang, L.; Yang, W.; Fu, S.; Elaïssari, A.

2003-02-01

441

Synthesis of graft copolymers based on poly(2-methoxyethyl acrylate) and investigation of the associated water structure.  

PubMed

Graft copolymers composed of poly(2-methoxyethyl acrylate) are prepared employing controlled radical polymerization techniques. Linear backbones bearing atom transfer radical polymerization (ATRP) initiating sites are obtained by reversible addition-fragmentation chain transfer copolymerization of 2-methoxyethyl acrylate (MEA) and 2-(bromoisobutyryloxy)ethyl methacrylate (Br(i) BuEMA) as well as 2-hydroxyethyl methacrylate and Br(i) BuEMA in a controlled manner . MEA is then grafted from the linear macroinitiators by Cu (I)-mediated ATRP. Fairly high molecular weights (>120 000 Da) and low polydispersity indices (1.17-1.38) are attained. Thermal investigations of the graft copolymers indicate the presence of the freezing bound water, and imply that the materials may exhibit blood compatibility. PMID:22271568

Javakhishvili, Irakli; Tanaka, Masaru; Ogura, Keiko; Jankova, Katja; Hvilsted, Søren

2012-01-23

442

High temperature structural, polymeric foams from high internal emulsion polymerization  

SciTech Connect

In 1982, a high internal phase emulsion (HIPE) polymerization process to manufacture microcellular, polymeric foam systems was patented by Unilever. This patent discloses a polymerization process that occurs in a water-in-oil emulsion in which the water represents at least 76% of the emulsion by volume. The oil phase consists of vinyl monomers such as styrene and acrylates that are crosslinked by divinyl monomers during polymerization. After polymerization and drying to remove the water phase, the result is a crosslinked polymer foam with an open cell microstructure that is homogeneous throughout in terms of morphology, density, and mechanical properties. Since 1982, numerous patents have examined various HIPE polymerized foam processing techniques and applications that include absorbents for body fluids, cleaning materials, and ion exchange systems. All the published HIPE polymerized foams have concentrated on materials for low temperature applications. Copolymerization of styrene with maleic anhydride and N-substituted maleimides to produce heat resistant thermoplastics has been studied extensively. These investigations have shown that styrene will free radically copolymerize with N-substituted maleimides to create an alternating thermoplastic copolymer with a Tg of approximately 200{degrees}C. However, there are many difficulties in attempting the maleimide styrene copolymerization in a HIPE such as lower polymerization temperatures, maleimide solubility difficulties in both styrene and water, and difficulty obtaining a stable HIPE with a styrene/maleimide oil phase. This work describes the preparation of copolymer foams from N-ethylmaleimide and Bis(3-ethyl-5-methyl-4-maleimide-phenyl)methane with styrene based monomers and crosslinking agents.

Hoisington, M.A.; Duke, J.R.; Apen, P.G.

1996-02-01

443

Femoral impaction grafting.  

PubMed

Femoral impaction grafting is a reconstruction option applicable to both simple and complex femoral component revisions. It is one of the preferred techniques for reconstructing large femoral defects when the isthmus is non-supportive. The available level of evidence is primarily derived from case series, which shows a mean survivorship of 90.5%, with revision or re-operation as the end-point, with an average follow-up of 11 years. The rate of femoral fracture requiring re-operation or revision of the component varies between several large case series, ranging from 2.5% to 9%, with an average of 5.4%. PMID:23362469

Scanelli, John A; Brown, Thomas E

2013-01-18

444

Femoral impaction grafting  

PubMed Central

Femoral impaction grafting is a reconstruction option applicable to both simple and complex femoral component revisions. It is one of the preferred techniques for reconstructing large femoral defects when the isthmus is non-supportive. The available level of evidence is primarily derived from case series, which shows a mean survivorship of 90.5%, with revision or re-operation as the end-point, with an average follow-up of 11 years. The rate of femoral fracture requiring re-operation or revision of the component varies between several large case series, ranging from 2.5% to 9%, with an average of 5.4%.

Scanelli, John A; Brown, Thomas E

2013-01-01

445

Synthesis and characterization of Gd@C82-PVK and C60-PVK--a kind of fullerene-grafted polymer.  

PubMed

Different fullerene-grafted poly(N-vinylcarbazole) was synthesized by free radical polymerization and the influence of the amount of initiator, the reaction time and the reaction temperature on the polymerization was studied. Metallofullerene-grafted polymer (Gd@C82-PVK) was firstly synthesized and characterized by GPC, UV-vis, FTIR, DSC, XPS. The results demonstrated that the fullerenes had chemically combined with PVK. Fluorescence spectra suggested that the grafted fullerenes had certain influence on the fluorescence properties of the polymer. This is due to the better electron-attractive ability of fullerenes, which contributed a lot to form the electron donor-acceptor systems in fullerene-grafted poly(N-vinylcarbazole). Potential applications of this kind of materials in optical and memory devices were expected. PMID:23035458

Ruan, Xiaolin; Yue, Dongmei; Yang, Shangyuan; Guo, Xihong; Dong, Jinquan; Cui, Rongli; Sun, Baoyun

2012-09-01

446

Switchable Adhesion from Bicomponent Polymeric Brushes  

NASA Astrophysics Data System (ADS)

We investigated the adhesive and wetting properties of bicomponent polymeric brushes made from end functionalized hydrophilic and hydrophobic polymer chains. The molecular organization of the mixed brush could be varied reversibly by exposure to selective solvents for the two polymers. Adhesive properties were tested by debonding a flat ended probe from soft pressure-sensitive-adhesives (hydrophobic & hydrophilic) and wetting properties were tested by contact angle measurements of water & diiodomethane droplets. The bicomponent brushes were chemically grafted on silicon wafers from end-functionalized chains. Wetting experiments were done directly on the wafers while for adhesion experiments, the wafers were glued on the flat end of the probe prior to the tests. In all cases the organization of the bicomponent brush could be modified reproducibly and reversibly by exposure to selective solvents. Following this strategy we succeeded to create remarkably stable adaptive polymer surfaces that can modify their adhesion and wetting reversibly and also tune them by varying the ratio of the bicomponent brush layer.

Retsos, Haris; Gorodyska, Ganna; Creton, Costantino

2005-03-01